A weight (4) which is held by a weight holder (3) in a balancer has a pressing face (4b') which is pressed against a guide face (12a) provided along the circumferential direction of rotation of the weight holder (3) by centrifugal force generated by rotation of a rotary body. When the rotary body rotates, the weight (4) which is pressed against the guide face (12a) via the pressing face (4b') changes its position relative to the rotary body in the circumferential direction of rotation, whereby the weight (4) is disposed in a position in which it suppresses whirling motion of the rotary body. The guide face (12a) and pressing face (4b') are inclined relative to the axial direction of rotation so as to tend to outward side in the diametrical direction of rotation as tending to one side in the axial direction of rotation. The weight (4) is pressed against a receiving portion (7a') by component of the centrifugal force, in which the component acts along the guide face (12a) and pressing face (4b').