To stability a frequency control voltage sensitivity of a strip line by eliminating the need for a capacitor for adjusting the frequency control voltage sensitivity and simplifying a resonance circuit section.

The voltage controlled oscillator circuit is provided with a resonance circuit section, a negative resistance circuit section and an amplifier circuit section, and the resonance circuit section is made up of a strip line conductor film 1 (consisting of a curved part 1a and a trimming region 1b) of a nearly U-shape whose one end 3 connects to ground and whose other end 4 connects to the negative resistance circuit section and up of a varicap diode Cv connecting to an outer circumference of the curved part 1a of the strip line conductor film 1 and receiving a control voltage. As this adjustment method, the resonance frequency of the resonance circuit section is adjusted by selectively removing an inner circumferential part of the curved part so as to reduce a conductor width of the curved part 1a of the U-shaped strip line conductor film 1.