To provide a monocoque structure piston opposing type caliper body of a disk brake for a vehicle for securing rigidity and heat discharging property of a bridge part and downsizing the caliper body without deteriorating fluidity in casting.

On the disk rotating directional both end sides of a first ceiling opening 9 and a second ceiling opening 10 in the caliper body 3, four opening corner parts 9a, 9a, 10a, and 10a are formed into circular arc shape. Two disk axial surfaces 9b and 10b continuing to the opening corner parts 9a, 9a, 10a, and 10a are protruded to the center side of the ceiling opening parts 9 and 10 beyond outside torque receiving surfaces 3k and 3m arranged on the disk rotating directional both end sides of the caliper body 3, and reinforcing parts 9c and 10c are formed on the outside torque receiving face sides of the disk axial surfaces 9b and 10b.