An optical signal to electrical signal converter of the present invention comprises an optical waveguide propagating a modulated optical signal therethrough; a pair of electrodes disposed at positions opposite to each other sandwiching the optical waveguide with in a region where an electric field reaches that is generated in the optical waveguide when the optical signal propagates through the optical waveguide; and a resonator coupled to the pair of electrodes, the resonator receiving for excitation an electrical signal induced at the pair of electrodes by the electric field.