To provide a disk brake which makes it possible to efficiently manufacture a brake caliper and a vehicle body side support portion, while maintaining the positioning accuracy of the brake caliper. A front disk brake includes a brake caliper provided with a pair of caliper side mount portions and a caliper bracket provided with a pair of bracket side mount portions. The brake caliper is fixed to the caliper bracket by mounting fastening bolts in bolt passing holes and screw holes formed respectively in the mount portions. The bolt passing holes and the screw holes are provided at their portions on the sides of opposed surfaces with counterbores in which collar members are to be fitted. The lower-side counterbore in the brake caliper is formed in an oblong sectional shape elongate in the arrangement direction of the lower-side counterbore and the upper-side counterbore paired therewith.