A brake device for a vehicle includes a brake pedal rotatably supported on a support shaft and extending in a front ward direction from the support shaft in the longitudinal direction of the vehicle. A master cylinder is located on the rear side of the support shaft in the longitudinal direction of the vehicle for generating a braking hydraulic pressure according to the rotational operation of the brake pedal. An operational amount detector is mechanically connected to the brake pedal for detecting the rotational amount of the brake pedal. The master cylinder includes an axis that is arranged vertically and is located above the support shaft with the operational amount detector being located on the rear side of the support shaft in the longitudinal direction of the motorcycle. Thus, the master cylinder and the operational amount detector can be densely arranged in the longitudinal direction of the vehicle.