In a thermally assisted magnetic recording head having a light source and a waveguide to lead a laser beam radiated from the light source to a front end of the magnetic head, while blocking an adverse effect of heat generated in the light source and securing a good floating characteristic, the light source and the magnetic head are optically coupled with high efficiency and the magnetic head itself is reduced in size. This invention provides a reflection mirror that is formed of a part or whole of one inclined end surface of the semiconductor laser mounted on the first submount. Near one end surface of the slider is provided the optical waveguide that pierces through the slider in a direction of the thickness thereof. The slider is mounted on the second submount and the positions of the first submount and the second submount are adjusted to practically align the light axis of the beam emitted from the mirror with the light axis of the optical waveguide, thereby realizing a novel thermally assisted magnetic recording head.