BRAKE DEVICE

A brake device to be applied to a vehicle includes a housing, a piston, and a seal member. The housing has a first end that is closed. The housing includes a supply port configured to communicate with a reservoir tank. The piston has an outer peripheral surface, an inner peripheral surface and a through-hole extending from the outer peripheral surface to the inner peripheral surface. The piston is configured to generate a hydraulic pressure in a hydraulic chamber in the housing by moving toward a side of the first end inside the housing. The seal member is provided around the piston in a circumferential direction on the side of the first end with respect to the through-hole. The seal member is configured to seal between an inner peripheral surface of the housing and the outer peripheral surface of the piston.