To strive cost reduction and improvement of reliability of a disk brake enabling processing of a cylinder arranged in a caliper by piercing from the cylinder bottom side and also having structure in which the cylinder bottom is closed by installing a cover.

A rivet portion 12 passing through a small diameter hole portion 10 arranged in the bottom side of the cylinder 2 is arranged in a cover 4, and the tip of the rivet portion 12 is crimped and fixed in the edge of an opening of the small diameter hole portion 10. Further, crimping work can be performed with small force so that a root (a) of the rivet portion 12 is entered into the front side of the cylinder more than a bending point (b) for crimping, and the cover is eventually prevented from jolting so as to make a seated surface 4a of the cover tightly stick to the caliper by means of pulling-in force generated during crimping work.