To provide an evaluation device of an on-vehicle collision mitigation system capable of repeated evaluation by suppressing each damage of a vehicle loaded with the collision mitigation system and a collision object.

A target member 20 with which the vehicle loaded with the collision mitigation system collides is supported by a connection arm 80, rotatably to the opposite side to the collision side of the vehicle by a rotation mechanism part 40. Resultantly, when the vehicle which is an evaluation object collide with the target member 20, the target member 20 is rotated to the opposite side to the collision side of the vehicle by the rotation mechanism part 40, and thereby a collision impact is mitigated. Consequently, since each damage of both the vehicle which is the evaluation object and the evaluation device is mitigated, repeated evaluation becomes possible.