The typhoon No.10 hit the Pacific cost in Hokkaido on August 9 in 2003. The casualties were 10 killed and 3 wounded. The missing person has not been found yet. This typhoon gave the biggest damage by flood to Hokkaido in the last twenty years. In Saru River basin and Appetu River basin in Ilidaka region, serious damages, such as flooded house, house failure and bridge fall, occurred by this typhoon. Farmland and flood plain were covered for the large sediment. In this paper, we will report an outline of heavy rainfall disasters of Hidaka region in Hokkaido by the typhoon No.10. We hope that the result of this investigation helps to clarify the mechanisms of the heavy rainfall disasters with hydrologic and hydraulic knowledge.