A pressure adjuster for changing pressure between a plurality of opposed bodies pressed against each other includes a cam rotatable in a given direction of rotation and having a top dead center on an outer circumferential surface thereof that is distanced farthest from a rotation axis of the cam. A driver is connected to the cam to drive and rotate the cam. A cam rest contacts the cam and is connected to one of the plurality of opposed bodies. A cam regulation assembly is connected to the cam to regulate rotation of the cam at least when the top dead center of the cam passes a contact position where the cam contacts the cam rest.