A direct acting pressure reducing valve includes a valve-inlet pressure introduction port; a valve-outlet pressure output port; a main valve for opening and closing a communicating conduit; a pilot pressure chamber formed with a flexible diaphragm member; a communicating hole; a connecting rod inserted in the communicating hole; and a biasing member for biasing the flexible diaphragm member in a direction to open the main valve. An insertion portion of the connecting rod has a partly-deformed circular cross section, a distance from a deformed portion thereof to a center of an imaginary circle corresponding to the communicating hole being shorter than a radius of the imaginary circle. A non-deformed portion of the partly-deformed circular cross section guides the connecting rod along the communicating hole, while the deformed portion serves as an air passage via which the communicating conduit and the pilot pressure chamber are communicatively connected.