An experimental study of local scour around a seaside single house and a group of houses by tsunami waves was carried out in a wave tank. The experimental results show that local scour occurs around the house, especially on the sea side due to a hydraulic drop generated by tsunami wave overtopping and the disturbed flow generated by tsunami waves passing through the house. The hydraulic drop is the main cause of local scour and disturbed flow is the secondary cause. For a single house, the empirical relationship between the relative maximum scour depth and relative overtopping height of the tsunami wave was established. For a group of houses, the empirical relationships between the maximum local scour depth and the tsunami wave height, house width, house height, the number of houses, and center spacing of houses were established. The internal relation between the maximum local scour depth and the incident wave height, house size and layout was determined.