The electrode substrate 401 has integrally applied thereon an LD (laser diode, as used herein) chip 402 as a light emission source, a photo diode 403 joined to an LD mount 404 for monitoring a light quantity, a drive circuit formed on a bare chip 408 for use to the light emission source, a drive circuit formed on a bare chip 405-1 for use to a deflection unit, and other components such as resistor