A method of manufacturing a thermally-assisted magnetic recording head includes: providing a light source unit including a laser diode; providing a slider having a thermally-assisted magnetic recording head section thereon, the thermally-assisted magnetic recording head section including a magnetic pole, an optical waveguide, and a plasmon generator, the magnetic pole and the optical waveguide both extending toward an air bearing surface, the plasmon generator being located between the magnetic pole and the optical waveguide; driving the laser diode to allow a light beam to be emitted therefrom, the light beam including both a TE polarization component and a TM polarization component; performing an alignment between the light source unit and the thermally-assisted magnetic recording head section, based on a light intensity distribution of the TE polarization component in the light beam which has been emitted from the laser diode and then passed through the optical waveguide; and bonding the light source unit to the slider after the alignment is completed.