To reconcile (1) to keep stability of a rotating speed high in a low load area LL and (2) to reduce a coefficient of variation of a permanent speed in a high load area LH.

In a state where a governor lever 3 exists in a full-load position 4/4, the coil axis 10 of an idle spring 5 made of a tension coil spring is inclined at a spring inclination opening angle θ0 of an acute angle to the lever rocking directional axis 9. The spring inclination opening angle θ0 becomes large as the governor lever 3 approaches the full-load position 4/4 from a no-load position 0/4. In a state where the governor lever 3 exists in the full-load position 4/4, the spring inclination opening angle θ0 is set in an angle range of 30 degrees to 40 degrees.