A semiconductor integrated circuit includes a mixer circuit unit having a first single gate mixer configured to receive a first input signal having a first frequency and a second input signal having a second frequency as inputs, a second single gate mixer configured to receive the first input signal and a third input signal of a phase inverted from a phase of the second input signal as inputs, a third single gate mixer configured to receive a fourth input signal of a phase inverted from the phase of the first input signal and the second input signal as inputs, and a fourth single gate mixer configured to receive the third and the fourth input signals as inputs; and a 1/2-frequency divider unit configured to receive output signals from the first to the fourth single gate mixers as inputs and output a desired signal.