A high power type voltage controlled oscillator (VCO) includes (a) an input terminal for receiving a controlling voltage, (b) a voltage controlled oscillating section (VCO section) to which the controlling voltage is supplied, (c) a power amplifier to which an output from the VCO section is supplied, (d) a matching circuit to which an output from the power amplifier is supplied, (e) an output terminal to which an output from the matching circuit is supplied, (f) inspection means for adjusting or inspecting independently the VCO section and the amplifier, (g) interference preventive means for preventing interference from the amplifier to the VCO section, (h) a heat sink for dissipating heat generated by the amplifier to outside, and (i) a board in which the elements described in (a)-(h) are accommodated. This structure allows a device such as a cellular phone to be assembled with higher productivity as well as downsized.