A pressure reducing valve includes a piston disposed in a cylinder chamber; a valve element that is coupled to the piston and opens and closes a valve seat; a valve spring that biases the valve element in a direction in which the valve element is moved away from the valve seat; and a biasing member that biases the valve seat toward a side opposite to the piston. The pressure reducing valve is configured to reduce a primary pressure of a fluid to a secondary pressure. The valve seat is disposed such that the valve seat reciprocates in the same direction as a direction in which the valve element reciprocates in the primary pressure chamber. As a difference between the primary pressure and the secondary pressure increases, the valve seat moves toward the secondary pressure chamber.