A video IF signal detector includes a first phase detector detecting a phase difference between an input video IF a signal and a first reference signal. A low pass filter acts on an output signal from the first phase detector. A VCO generates the first reference signal and a second reference signal in response to an output signal from the low pass filter. The first reference signal and the second reference signal have a fixed phase relation with each other. The first phase detector, the low pass filter, and the VCO compose a PLL. A second phase detector detects a phase difference between the input vido IF signal and the second reference signal and extracts a baseband video signal from the input video IF signal. The PLL is enabled during a first period where the input video IF signal is independent of display information. The PLL is disabled during a second period where the input video IF signal represents the display information.