Pressure reduction valve

A pressure reduction valve, comprising:

• a body including a gas passage;
• a valve seat provided in the gas passage;
• a valve member provided on a downstream side of the valve seat in the gas passage, wherein the gas passage includes:
• a primary-side passage section located on an upstream side of the valve member;
• and a secondary-side passage section located on a downstream side of the valve member, the primary-side passage section includes a pressure chamber, the pressure chamber being a space formed between the valve member and the valve seat, the valve member is configured to be constantly urged in a direction away from the valve seat and to open and close the valve seat in accordance with a difference between a pressure in the primary-side passage section and a pressure in the secondary-side passage section, the valve member further includes:
• a valve member passage that opens in an outer circumferential surface of the valve member and connects the pressure chamber to the secondary-side passage section, and an auxiliary passage that opens in the outer circumferential surface of the valve member and is configured to increase an amount of gas that flows into the pressure chamber through a clearance between the valve member and the valve seat to flow out to the secondary-side passage section compared to a valve member without an auxiliary passage, the valve member passage and the auxiliary passage open independently from each other in the outer circumferential surface of the valve member, and a first opening of the auxiliary passage is positioned in the outer circumferential surface of the valve member, the first opening of the auxiliary passage being upstream with respect to a first opening of the valve member passage along a direction in which the gas flows.