To provide a linear light source producing linear light usable in a micro region.

The light source uses light which is produced by using an exciting source for exciting a phosphor in a close contact with a plate transparent body. The transparent body has the face with which the phosphor is in a close contact, as an incident plane for the light emitted by the phosphor, and an end face other than the face with which the phosphor is in a close contact, as an output plane. It is used for emitting the excitation light to the phosphor which is in a close contact with part of the transparent body to take the light emitted by the phosphor from the output plane of the transparent body.