To effectively prevent reception signals from sneaking in and to enter a large signal route, from a small signal route, at a low cost using a simple configuration, in order to improve NF characteristics, in addition to improving the sensitivity of reception and widening the dynamic range.

A signal S1 on the small signal route branched by a directional coupler 205 is input to a mixer 202 via a low-noise amplifier 201, and a low-gain signal S2 on the large signal route is input to a mixer 207, and then intermediate frequency signals are taken out of mixed signals, respectively. A local oscillating signal, generated by a local oscillator 203, is distributed and applied to the mixers 202, 207 by using a distributor 206, such that applying on the mixer 202 side is carried out with zero gain, by transmitting the signal through a series circuit comprising an attenuator 209 and an amplifier 210. The gain of the low-noise amplifier 201 is offset by the negative gains of the attenuator 206 and the amplifier 210 in a direction from the mixer 202 to the distributor 206, thereby preventing the signal S1 on the small signal route from turning so as to enter the large signal route side.