PURPOSE: To stabilize the operation of a radar apparatus by controlling the gain of an RF amplifier, thereby setting an IF signal reliably within the operating frequency band.

CONSTITUTION: The gain of an RF amplifier of a radar receiver 11 is controlled synchronously with a transmission radar signal from a magnetron 1, so that the changing amount of the frequency of a local oscillator is restricted. Therefore, even when a radar signal of the excessive power such as the transmission radar signal enters the radar receiver 11, the radar signal leaking to the local oscillator is attenuated and the change of the locally emitted frequency is reduced. An IF signal is thus set within the band of the operating frequency.