PURPOSE: To provide a dimming controller for head lamp of a motor-bicycle which can prevent the consumption of battery power without using a large-sized generator while maintaining the object of improving the visibility from ahead by a normally lit head lamp.

CONSTITUTION: A device for controlling the head lamp of a motor-cycle equipped with a normally lit head lamp 14, a hazard switch 24 for lighting a hazard lamp, and a side stand has a side stand switch 40 for detecting the housing condition of the side stand, a hazard switch 24 for switching the hazard lamp to hazard indication state, and a head lamp relay 48 for putting out the head lamp 14 when the hazard switch 24 is switched to hazard indication state, when the housing state of the side stand is not detected.