To provide a head lamp for a vehicle of which the failures hardly occur as well as the inside structure is compact.

This head lamp for a vehicle comprise a gas discharge lamp 10 of which the bulb 12 is disposed at the front end of a bobbin 11, a spherical reflection mirror 20 for surrounding the back of the gas discharge lamp 10 to reflect the light emitted from the gas discharge lamp 10 forward, a housing 30 for holding the gas discharge lamp 10 so as to be longitudinally slidable in the housing 30, a lamp sliding means 50 for switching the lamp between a high beam and a low beam by sliding the position of a bobbin 11 in the housing 30, compression spring 5 for resiliently biasing the bobbin 11 in the direction forward, a magnet assembly 52 disposed at the backside of the housing 30 so as to be adjacent to the backside of the bobbin 11, and a solenoid 53 wound at the backside of the bobbin 11 so as to make the bulb 12 slide backward with the bobbin 11 by the interaction with the magnet assembly 52 when supplying power.