A variable gain amplifier (1) includes: a signal transmission circuit (10, 20) including amplifying transistor units (11 1 to 11 N , and 21 1 to 21 N ) connected in parallel between a signal input port (2P, 2N) and a signal output port (3P, 3N); a load circuit (40) connected between a supply line of power supply voltage (VDD) and an output end of the signal transmission circuit (10, 20); a signal short circuit (30) including a short-circuit transistor unit (31) connected between the supply line of the power supply voltage (VDD) and an input end of the signal transmission circuit (10, 20), a constant-current source circuit (42), and a transistor control circuit (46). The transistor control circuit (46) selects transistor units to be turned on, from among the amplifying transistor units (11 1 to 11 N , and 21 1 to 21 N ) and the short-circuit transistor unit (31), and supplies control voltages for turning on the selected transistor units.