PURPOSE: To provide an optical head, optical disk device using the same and propagating prism used for the same for which the shape can be made thin, the configuration can be simplified, the 'manufacturing process can be simplified and the number of parts to be adjusted is reduced.

CONSTITUTION: The prism is composed of a reference plane A to be faced to the propagating direction of light while keeping the almost parallel state, reflecting plane B and rise mirror plane C to be continued while keeping a planned angle θ with the reflecting plane B, the light from a light source 1 is propagated between the reference plane A and the reflecting plane B while repeating full reflection, reflected on the rise mirror plane C later and perpendicularly transmitted through an exit light position A2 as one part of the reference plane A. The inclination angle α of the rise mirror plane C is set so that one part of a reflecting position A1 on the reference plane A can be overlapped with one part of the exit light position A2 on a preceding stage to the rise mirror plane C.