The reflection portion of the reflection member is moved along the inner surface in the hole of the pipe from the entrance opening of the hole of the pipe to the exit opening of the hole thereof. In this case, the reflection portion is guided by the guide portion provided at both sides of the reflection portion. The shots, which are projected toward the inner surface in the hole of the pipe, reach the reflection portion through the holes of the guide portion of the entrance side, and they are reflected toward the inner surface in the hole of the pipe. Since the shots can be reflected toward the inner surface inside in the hole of the pipe, the tendency that shots may be moved toward the inner surface outside in the hole of the curved portion can be small.