Provided are an orifice member, and a differential-pressure flow meter and a flow-regulating device using the orifice member, that allow purging to be carried out easily when changing the fluid to be circulated, that are less likely to cause contamination and leaching of impurities to the circulated fluid, and that can be easily produced. The flow-regulating device includes a first pressure-measuring device (object to be connected to) that is connected to one end of the orifice member, and a second pressure-measuring device (object to be connected to) that is connected to the other end of the orifice member, and a flow-regulating valve that is connected to the downstream side of the differential-pressure flow meter, which includes the above-mentioned units. In the orifice member, a tube portion, one end of which is connected to the first pressure-measuring device and other end of which is connected to the second pressure-measuring device and whose internal part forms a channel connecting the first and second pressure-measuring devices, and an orifice provided inside the tube portion are integrated.