Total population170,780people
Households84,261households
Average age47.2yrs
Sex ratioMale89,436peopleFemale81,344people52.4%47.6%
Population change
Change over time
4-year trendUnit: people
176,512 in 2022170,780 in 2026
Down 3.2% over the past 4 years.
Migration
As of August 2026Monthly Overview
Moved in1,298people
Moved out1,575people
Net migrationβ277people
Net migration by month
Unit: people
Net inflowNet outflow
Top origins
Unit: people
| Region | Moved in |
|---|---|
| Taean-gun | 55 |
| Dangjin-si | 34 |
| Pyeongtaek-si, Gyeonggi | 28 |
| Cheonan-si | 28 |
| Ansan-si, Gyeonggi | 19 |
Top destinations
Unit: people
| Region | Moved out |
|---|---|
| Dangjin-si | 84 |
| Cheonan-si | 43 |
| Pyeongtaek-si, Gyeonggi | 34 |
| Asan-si | 34 |
| Hongseong-gun | 34 |
Outflows exceeded inflows in every one of the past 12 months, for a net loss of 1,678.
Population structure
Population by age
As of September 2026Population by age and sex
Unit: people
Male 89,436Female 81,344
Age structure
Unit: %
Youth 10.6%Working age 64.7%Seniors 24.7%
50s is the largest group, at 29,639 people.
Population ranking
Population by region
As of September 2026- YoungestYecheon-dong36.9 yrs
- OldestPalbong-myeon64 yrs
| Region | Share | ||
|---|---|---|---|
| Dongmun-dong | 23,883 | 14% | 47 yrs |
| Yecheon-dong | 23,448 | 13.7% | 36.9 yrs |
| Seongyeon-myeon | 16,956 | 9.9% | 37.4 yrs |
| Eumnae-dong | 15,636 | 9.2% | 45.1 yrs |
| Seongnim-dong | 15,625 | 9.1% | 42.2 yrs |
| Daesan-eup | 11,805 | 6.9% | 50.8 yrs |
| Eumam-myeon | 8,826 | 5.2% | 54.6 yrs |
| Jigok-myeon | 7,477 | 4.4% | 51.8 yrs |
| Haemi-myeon | 7,054 | 4.1% | 55.8 yrs |
| Inji-myeon | 6,886 | 4% | 53.2 yrs |
| Seongnam-dong | 5,706 | 3.3% | 44.3 yrs |
| Gobuk-myeon | 5,400 | 3.2% | 54.5 yrs |
| Buseok-myeon | 4,942 | 2.9% | 63.4 yrs |
| Unsan-myeon | 4,810 | 2.8% | 62 yrs |
| Palbong-myeon | 3,177 | 1.9% | 64 yrs |
| Jukseong-dong | 2,915 | 1.7% | 46.1 yrs |
| Galsan-dong | 1,623 | 1% | 50.6 yrs |
| Suseok-dong | 1,599 | 0.9% | 55.8 yrs |
| Yangdae-dong | 915 | 0.5% | 56.5 yrs |
| Onam-dong | 664 | 0.4% | 57.8 yrs |
| Jang-dong | 470 | 0.3% | 60.2 yrs |
| Onseok-dong | 426 | 0.2% | 56.7 yrs |
| Jamhong-dong | 408 | 0.2% | 56.4 yrs |
| Deokjicheon-dong | 129 | 0.1% | 62.3 yrs |
The top three areas hold 37.6% of the population of Seosan-si, Chungcheongnam-do.
Frequently asked questionsβ
Seosan-si, Chungcheongnam-do has 170,780 residents as of September 2026., 2,182 fewer than a year earlier.
Dongmun-dong, home to 23,883 residents (14.0% of Seosan-si, Chungcheongnam-do).
It is 47.2 as of September 2026., 1.5 years above the national average of 45.7. Among its neighborhoods, Yecheon-dong is youngest at 36.9 and Palbong-myeon oldest at 64.
It fell 3.2% over 4 years, from 176,512 in 2022 to 170,780 in September 2026.
As of August 2026, the most people moved in from Taean-gun (55) and the most moved out to Dangjin-si (84). Outflows exceeded inflows in every one of the past 12 months, for a net loss of 1,678.
This is resident registration data from Korea's Ministry of the Interior and Safety. Figures are as of the end of September 2026 and are updated monthly. The data is open under KOGL Type 1.
Resident registration counts people at their registered address. The census counts them where they actually live. The gap is widest in university towns and industrial areas, where many people never change their registered address.
Sources π
- Resident registration data, Ministry of the Interior and SafetyKOGL Type 1 Β· as of September 2026 Β· updated monthly
- Internal Migration Statistics, Statistics Korea (KOSIS)KOGL Type 1 Β· as of August 2026 Β· updated monthly