<p>A brake fluid pressure controller is interposed between a master cylinder and the rear wheel cylinders. The controller comprises a housing having an inlet, an outlet and a chamber which provides communication between the inlet and the outlet. An annular sealing member is disposed around a piston in the chamber with a clearance left therebetween. The sealing member has an inner perimeter defining a valve seat and an outer perimeter defining a flexible lip portion which is in contact with the internal wall of the chamber. When a valve head of the piston sits on the valve seat of the sealing member, the inner perimeter of the valve seat cuts off the communication between the inlet and the outlet. Meanwhile, the outer perimeter permits a communication from the outlet to the inlet but shuts off a communication from the inlet to the outlet. A spring urges the piston to a direction in which the valve head separates from the valve seat. A regulating member contacts the inner perimeter of the sealing member in the chamber from a side opposite to the valve head. The regulating member regulates the sealing member from moving in a direction from the valve head toward the regulating member.</p>
