To provide a governor mechanism for a diesel engine which increases a starting increment of fuel so as to secure sufficient startability, and to control an engine speed at an arbitrary speed.

A governor mechanism for a diesel engine, wherein a tension lever 2 urged with a governor spring 3 is engaged to a governor lever 5 connected to a control rack 7 with both an engaging hole 8 and an engaging rod 9 above a governor shaft 1 so as to be rotated together, is provided with an electromagnetic actuator 12. The electromagnetic actuator 12 presses the governor lever 5 depending on a signal from a controller 13 until a engine speed reaches a prescribed speed after an engine starts, so as to increase the starting increment of fuel.