In a low noise amplifier circuit of a wide band for use in a multi-channel receiving system, it is arranged that the resonance frequency of a load part (2) comprising a variable capacitor (9) and an inductor (10) be made coincident with a desired RF signal frequency by controlling the capacitance value of the variable capacitor (9) by use of a resonance frequency control circuit (4). This arrangement allows both a high gain and a wide band to be achieved at the same time without increasing the power consumption. As a result, a receiving system can be provided which exhibits a low power consumption and a high sensibility for all channels.