The signal converter of the present invention receives a multichannel video signal and converts the video signal into a microwave signal, the phase of which has been modulated with the video signal. The signal converter includes: a laser light source; a modulating section for modulating the phase of output light of the laser light source with the multichannel video signal and modulating the intensity of the output light with the microwave signal; and a light receiver for receiving the output light modulated by the modulating section and for outputting the microwave signal, the phase of which has been modulated with the multichannel video signal.