Global sea level change patterns represent an average of gradual temporal changes occurring across wide areas. However, localized sea level change patterns can differ significantly. In the Republic of Korea, for instance, sea level rise along its coasts notably exceeds the global average. The specific patterns of mean sea level (MSL) change vary considerably by sea area (e.g., east, west, south, and Jeju) owing to regional differences in influencing factors. This is evident in the diverse rates of sea level rise; the west sea records the lowest at 1.36 mm/year, whereas the Jeju sea area has the highest at 5.81 mm/year, a difference of approximately 4.3 times. Crucially, the recent acceleration in sea level rise, when combined with these regional variations, where temporal and spatial changes converge, can intensify the rise, potentially creating areas highly vulnerable to sea level rise. In this study, we analyze sea level changes along the coast of South Korea using long-term tidal observation data collected at one-hour intervals from coastal tide gauge sensors. These sensors continuously measure the sea surface at a high temporal resolution (hourly), providing essential data for monitoring changes in the marine environment. Unlike past research in which MSL rise (or fall) was estimated by simply taking the arithmetic mean of observation data, our approach facilitated a sea level change analysis that simultaneously considered both temporal and spatial variations using tidal data that accounted for only long-period components. A prominent finding of the analysis is that the amount of sea level rise on the west coast of South Korea increases from the north (Yeongjong Bridge) to the south (Mokpo). The fact that sea level rise due to the long-period components (with short-period components excluded) is greater in the south (Mokpo) suggests that, from a long-term perspective, the change in MSL could be more significant in the southern region of the west coast than in the northern part.