A disk brake and a method of making the disk brake capable of improving the efficiency of manufacturing a caliper. A bottom portion (41) of a bore (40) is formed by integrally welding an opening surrounding portion at the bottom portion side of a cylinder portion (35) and a bottom cover member (92) fitted to the opening surrounding portion by friction stir welding. The bottom cover member is formed into a disk shape, and provided with a protrusion (68) at one surface side facing the interior of the bore. An inflow hole (58), for a supply of a fluid pressure into the bore, is formed within the range of the protrusion to establish communication between an interior surface (71) of the protrusion and an outer surface (63) of the bore.