A speed ratio detecting valve means of torque converter comprising a hub of a stator vane spline fitted onto a fixed shaft and being freely rotatable through a prescribed play angle, the hub being permitted to rotate relative to the fixed shaft by said play angle at a prescribed speed ratio utilizing a phenomenon that the direction of force of a working fluid in the torque converter exerted on the stator vane is reversed when an input-output rotation speed ratio reaches said prescribed value, and causing a fluid passage opening through a fixed shaft inside to an outer periphery of the fixed shaft to joint with or shut off from its jointing part.