Yoshioka-Kaitei Station was a railway station on the Kaikyo Line in Fukushima, Hokkaido, Japan, operated by Hokkaido Railway Company. The station was underground and was located within the Seikan Tunnel under the Tsugaru Strait linking the main Japanese island of Honshu with the northern island of Hokkaido. The station was located 149.5 metres (490 ft) below sea level, making it the deepest underground station in the world.