On the western coast of Hokkaido, Japan, kelp beds dominated by Saccharina japonica var. religiosa are restricted to shallow waters and spatially separated from offshore urchin-dominated barren grounds. We investigated the spatial distribution of kelp zoospores, water currents, and the distribution of kelp beds at Tomari on the coast. Zoospore motility was evaluated in the laboratory at water temperature 7.5, 10.0, 12.5, 15.0, and 17.5℃. At the sea surface, water current direction ranged mainly from northward to westward with velocities of 3.2-6.2 km・day^<-1> (estimated by current meter) and 2.5-3.8 km・day^<-1> (estimated by drifting buoys). Zoospore motility at water temperature in November at Tomari was estimated at 12 hr. Based on the data of drifting buoy and zoospore motility, the maximum potential distance of zoospore dispersal was estimated as 1.3-1.9 km. On the other hand, kelp zoospores were detected at a maximum distance of 1200 m from the closest kelp source population in cultures using sampled seawater. Zoospore densities rapidly declined with increasing distance from the source kelp bed. This study demonstrated that the dispersal potential of the kelp zoospore is more restricted than previously thought.