A thermally assisted magnetic head has a slider having a medium-facing surface, and a light source unit having a light source support substrate, and a light source disposed on the light source support substrate. The slider has a slider substrate and a magnetic head portion disposed on a side of the medium-facing surface in the slider substrate; the magnetic head portion includes a magnetic recording element for generating a magnetic field, and a waveguide for receiving light through an end face opposite to the medium-facing surface, and guiding the light to the medium-facing surface; the light source support substrate is fixed to a surface opposite to the medium-facing surface in the slider substrate so that light emitted from the light source can enter the end face of the waveguide.