A master cylinder

A master cylinder is provided with a resin-made cylinder main body (2) formed with a stepped portion (2c) at a boundary between a cylinder hole (2a) and a mount hole (2b), a piston (3) defining a hydraulic chamber (14) in cooperation with the inner circumferential surface of the cylinder hole (2a), a guide sleeve (8) adapted to guide a base end portion of the piston and locked in the cylinder main body (2) by a locking device, a first annular sealer (10) which has an inner seal member (10a) made of a soft material and an outer seal member (10b) made of a hard material held on the outer circumferential surface of a leading end portion of the piston, and a second annular sealer (17) squeezed between the stepped portion and a leading end portion of the guide sleeve (8). At least a portion of the outer circumferential surface of the piston (3) to be held in contact with the second annular sealer is made of a metal. There can be provided an inexpensive master cylinder capable of suppressing an occurrence of squeak and rattle caused by the stick-slip phenomenon.