PISTON FOR DISK BRAKE

PROBLEM TO BE SOLVED: To maintain the thickness of a boot groove part and to reduce weight by providing the boot grove in an outer periphery to be engaged with a main body member and also providing a pressing member contacted with a pad. SOLUTION: An engaging part 3e engaged with a pressing member 5 is provided in the end part of a cylindrical part 3c. Here, the thickness of the cylindrical part 3c is made thin as much as possible within the limit of a strength. On the other hand, the pressing member 5 includes, in addition to a boot groove part 5a, a step part 5b engaged with the engaging part 3e of the main body member 3. As a method of engaging the engaging part 3e of the main body member 3 with the step part 5b of the pressing member 5, a method of pressing the step part 5b into the engaging part 3e, or a method of gradually inserting the step part 5b into the engaging part 3e is used. In this case, since both surfaces of a piston 1 are held between a brake fluid and a pad always in its axial direction, the falling-off of the pressing member 5 from the main body member 3 is prevented.