A multichannel monolithic chip that has a number of photo-couplers provided on a single silicon substrate is mounted on an insulating substrate, a first cut groove is formed by dicing between a light-emitting element and a light-receiving element that constitute a photo-coupler, a transparent insulating resin is filled into the first cut groove and then a second cut groove is formed by dicing between the adjacent photo-couplers, each of the light-emitting element and the light-receiving element is electrically connected to an external terminal using a bonding wire, and the entirety of the insulating substrate is molded with a light-blocking resin.