A thermally assisted magnetic head includes a slider having a slider substrate and a magnetic head part, and a light source unit having a laser diode and a sub-mount. The magnetic head part includes a medium-opposite surface, a light source-opposite surface, and a slider-front end surface. The sub-mount includes a joined-end surface and a mount-front end surface, the laser diode includes an electrode surface and an LD-front end surface. The light source unit includes a shift joined structure which the laser diode is joined to a shift area of the joined-end surface, and the light source unit is mounted on the slider substrate so that the electrode surface intersects with a laminated surface of the magnetic head part. The shift area is set in a position which is shifted so that the LD-front end surface is away from the slider-front end surface than the mount-front end surface.