The manufacturing method for an electronic circuit device comprises attaching an electronic circuit assembly including a circuit substrate with electronic circuit elements attached to a base, joining lead terminals integrally with the base via frames before molding the lead terminals composed of a different material from that of the base with mold resin, electrically connecting the lead terminals to the electronic circuit assembly, molding the electronic circuit assembly, lead terminals, and flange with mold resin in a batch partially excluding the flange and lead terminals installed on the base, and separating and removing the frames from the lead terminals and base after the molding with the mold resin.