A rear brake control hydraulic master cylinder that dispenses with adjustment work to decrease a clearance between a piston and a push member. A master cylinder 31 includes first and second oil chambers. The piston includes a piston oil passage portion connected to the first and second oil chambers. The push member abuts against and moves the piston to generate a hydraulic pressure in the first oil chamber. A compression spring biases the push member into contact with the piston when the piston is not moved substantially toward the first oil chamber.