An obstacle detecting method and an obstacle detecting device for detecting an obstacle in a vehicle are disclosed. The obstacle detecting device according to the present invention detects a blind spot including the rear of the vehicle and includes: a sensing means for sensing an object placed in the blind spot including the rear of the vehicle; a rotating body having the sensing means therein and a rotating structure; and a washing means for washing the surface of the rotating body based on the degree of contamination on the surface of the rotating body.
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