PURPOSE: To obtain a phase locked circuit which can take greatly a phase margin, and also does not require an undesired wave low-pass filter by using a lug lead filter as a loop filter, and reducing an undesired wave.

CONSTITUTION: An output of a voltage control oscillator 4 is frequency-divided to a reference oscillation frequency by a frequency divider 5. Subsequently, an output of a reference oscillator 1 and an output phase difference of the frequency divider 5 are converted to a voltage by a phase comparator 2, and by a loop filter 3, a response characteristic of a feedback loop is determined and an undesired wave and a noise are reduced, and a desired output signal is obtained by controlling the voltage control oscillator 4. The loop filter 3 is a lug lead filter, and formed by combining a lug lead filter and a lug filter. That is to say, a resistance R1 is connected to one of connecting lines of an input terminal and an output terminal, and from one terminal of this resistance R1, a resistance R2 and a capacitor C1 are connected in series between the output terminals, and a capacitor C2 is connected in parallel to the resistance R2 and the capacitor C1.