Abstract The monthly mean tidal records for 31 years (1950 to 1980) from 86 tidal stations which are distributed around Japan and Korea were collected and analyzed. After the barometric correction was made by using the monthly mean pressure from the meteorological stations near the tidal stations, each tidal record was divided into 4 components: the linear trend, the mean annual variation, the fluctuation with periods longer than one year, and the fluctuation with periods shorter than one year. The maps showing characteristic properties such as the months of the highest and the lowest sea levels, and the range of mean annual variation were constructed. It was found that the Japanese and Korean coasts can be divided into 6 main regions and 14 subregions according to these maps together with the pattern of annual variations. The main regions and subregions represent specific coastal areas within which almost the same time scale of sea level variability can be seen. The map of the cross correlation coefficients between all the 86 stations also supports the above division of subregions. The spectral analyses of tidal records for the main tidal stations were also made.