Abstract: The master cylinder of the present invention is provided with the bearing in which a bearing body includes the inner circumferencial seal groove which is formed with a L-shape in longitudinal section with one side surface thereof opened, and a set plate is secured to an end surface of the bearing body so as to close the opened side surface of the inner circumferencial seal groove, wherein the set plate has a plurality of engaging pawls formed thereon for resiliently to pressing the bearing body onto a stopper ring or pressing the bearing body onto a step portion between a cylinder hole and the bearing housing while elastically holding the bearing body, whereby the seal member can easily be fitted into an inner circumferencial seal groove, of a bearing while preventing the bearing from chattering and preventing the seal member from being deformed seriously.