To provide a light source with high convergence efficiency independent of a setting state and provide an image projector using the light source by improving the structure of the light source such as a metal halide lamp.

A light source is constituted of a short arc metal halide lamp 2, a lamp reflector 3 for converging light, a support member 4, and a gravity detecting means 5 for linking and supporting a pair of permanent magnets 11, 12 arranged up and down with a linking means 14. When a weight 13 fixed to the linking means 14 is positioned downward, a pair of permanent magnets 12 on the lower side applies a horizontal transverse magnetic field C to a discharge arc to correct the discharge arc straight. The light source which is uniformly bright even in a reversed state at 180 degrees as in a standing state and an image projector using the light source are realized.