A disk brake includes a floating caliper, a pair of brake pads, a driving piston and a caliper return mechanism. The floating caliper includes a base portion which is slidably supported via a guide pin to a support and a pair of pressing arms which extend from the base portion to pinch a disk rotor. The brake pads are provided in tip portions of the pressing arms so as to face side surfaces of the disk rotor. The driving piston is provided on one of the pressing arms so as to drive one of the brake pads toward one of the side surfaces. The caliper return mechanism is arranged in at least one of both end portions of the guide pin on a side opposite to the driving piston side so as to elastically bias the base portion to the side opposite to the driving piston side.