To provide an amplifier circuit device which is high in reliability and low in cost by realizing an amplifier having an output attenuation function with a single power source operation, without complicating a manufacturing process.

This device is equipped with a transistor 1 which has a gate inputted by a signal and outputs its amplifier signal from a drain, a diode 2 connected forward between a source of the transistor 1 and a ground, and a control terminal 13 which are controlled via a resistor 3 and which makes a voltage lower than the forward direction potential of the diode. Then, by controlling a control voltage Vc which is added to a control terminal 13 in the vicinity of 0V, the gate voltage of the transistor 1 is made lower than that of the source of the transistor 1 that is put in relief by the forward potential of the diode 2 and output attenuation through off-isolation is realized.