There is provided a clutch mechanism that allows easy downsizing and produces favorable productivity. Output rotator has on the outer circumferential surface thereof cam surfaces and configured to gradually reduce the space from a housing chamber inner circumferential surface toward one side and recesses adjacent to the one side of the cam surfaces. Input rotator has pressure transmission portions that are fitted with circumferential play to the recesses and are protruded from the insides of the recesses in a centrifugal direction. Engagement pieces are disposed in contact with the cam surfaces and the housing chamber inner circumferential surface. When the input rotator rotates toward the other side relative to the one side, the pressure transmission portions abut against the engagement pieces and then abut against circumferential end surfaces in the recesses to press and move the output rotator.