To provide a flow control valve having a flow change rate constant with respect to a rotating angle even in multiple rotations and at any position without changing a flow rate even if the temperature changes.

This flow control valve includes an operation shaft and a housing 20 slidably fitted to each other, a spiral groove 14 forming a fluid passage on a slide surface of either of the operation shaft 12 and the housing 20, and an operation shaft moving mechanism axially moving the operation shaft 12 with respect to the housing 20. The spiral groove 14 is formed to gradually decrease or increase flow resistance of a fluid flowing through the flow passage in an exponential fashion obtained by Hagen-Poiseuille's formula along the longitudinal direction so that the rate of change of the flow rate of the fluid passage with respect to a certain travel distance of the operation shaft 12 is set constant when expressed by an exponential gradient at an optional axial position of the operation shaft 12, and the operation shaft 14 and the housing 20 are formed of materials having coefficients of thermal expansion different from each other.