Provided is a brake device capable of achieving highly responsive pressure increasing characteristics without being dependent on the discharge capacity of a pump. This brake device is provided with: an operating rod having a first diameter and operating in coordination with a brake operating member; a stepped piston having provided on one side thereof an intermediate-diameter section which has a diameter larger than the first diameter, a large-diameter section which has a larger diameter than the intermediate-diameter section, and an insertion hole into which the operating rod is inserted in the axial direction so as to be relatively movable; a first pressure chamber formed between the first diameter and the intermediate-diameter section; and a second pressure chamber formed between the intermediate-diameter section and the large-diameter section. The brake device controls the amount of supply of brake fluid to the first pressure chamber and the second pressure chamber and increases the amount of supply of the brake fluid to the second pressure chamber when there is a request for a highly responsive pressure increase.
