PURPOSE: To solve a problem of an operating area with simple constitution and to improve the transmission of a video signal by adding signals in terms of currents and supplying the result to an emitter coupling multivibrator.

CONSTITUTION: The FM modulator is provided with current source circuits 3A, 3B, 5A, 5B which are controlled respectively by an input video signal and signals resulting from the input video signal through a high pass filter 6. The currents from the current source circuits are added and the result is fed to an emitter coupling multivibrator comprising transistors(TRs) 1A, 1B and a coupling capacitor 2. Thus, a problem of a dynamic range due to the voltage is not caused and the signal resulting from the input video signal subjected to emphasis and frequency modulation is obtained at once with simple constitution.