To provide a flow meter, and a flow volume controlling device equipped therewith, capable of reducing pressure loss while obtaining a flow rectifying effect in a measurement fluid. A flow meter for measuring the flow volume of a measurement fluid, equipped with a flow path wherein the measuring fluid flows, and a flow rectifier that is disposed within the flow path, where the flow rectifier has holes for rectifying the flow of a measurement fluid, and has an area that is wider than the flow path cross-sectional area in a direction that is perpendicular to the direction in which the flow path extends. The flow volume controlling device is provided with the flow meter, a controlling valve, and controlling means for adjusting the flow volume of a fluid that flows through the flow path of the flow meter through controlling the controlling valves based on information regarding the flow volume detected by the flow meter.