A variable gain power amplifier includes a power amplifying unit and a signal generating unit. The power amplifying unit includes a control terminal, and a gain of the power amplifying unit is variable by a control signal provided through the control terminal. The signal generating unit generates the control signal to be provided to the control terminal. The signal generating unit includes a switching circuit to be turned on and off by a binary signal, a constant current source that generates a constant current, and a variable current source that generates a variable current. Also, the signal generating unit generates, when the switching circuit is on, a control signal of a magnitude that turns on the power amplifying unit and depends on a magnitude of a sum of the constant current and the variable current. When the switching circuit is off, the signal generating unit generates a control signal of a magnitude that turns off the power amplifying unit.