<p>A pressure reducing valve in which a diaphragm rod interconnected with a valve body of a valve mechanism is connected to the center of a diaphragm whose peripheral edge is held between a body and a diaphragm cover. The diaphragm (28) is constructed from a disc-shaped rubber plate whose thickness at least at its peripheral edge is uniform in a natural state. The peripheral edge of the diaphragm (28) is compressed and held between a flange (17b) of the diaphragm cover (17) and a holding surface (91) of the body (16), and thus the diaphragm cover (17) is fixed to the body (16). In this state, that portion of the diaphragm (28) which is located between the flange (17b) and the holding surface (91) and at which the gap between them is the smallest is located on the inside radially of that portion of the diaphragm (28) at which the gap is the largest. The construction reduces the weight and cost of the pressure reducing valve, improves sealing ability of the diaphragm, and prevents the diaphragm from coming out of place.</p>
