An optical pickup including a stem; a substrate mounted on the stem; a laser diode mounted on, and electrically insulated from, the substrate; and a photodetector provided on the substrate for detecting return light from an object to be irradiated. The substrate is biased at a given voltage and has an insulating member opposed to the stem. The laser diode has a first electrode opposed to the substrate with a first insulating film, a conductor film, and a second insulating film interposed between the first electrode and the substrate.