A system for performing posture control of a motorcycle is such that in outputting a synthesized output by adjusting a yaw direction output and a roll direction output outputted from a displacement detection sensor by an adjustment part respectively, a synthesized output in which the yaw direction output is larger than the roll direction output is outputted when a vehicle speed is low, and a synthesized output in which the roll direction output is larger than the yaw direction output is outputted when the vehicle speed is high. Accordingly, in either a case where the vehicle is traveling at a low speed or a case where the vehicle is traveling at a high speed, the displacement and the behavior of a motorcycle 10 can be detected with high accuracy thus eventually realizing a control of the posture of the motorcycle 10 with high accuracy.