A variable gain amplifier (VGA) with a linear-in-dB gain characteristic is provided. The VGA includes: a control signal converter which converts an input gain control signal VC, which is input so that the VGA obtains a linear-in-dB gain characteristic to the maximum gain, into an output gain control signal Vx=VTln((1/m)exp(−VC/VT)−1) (m is a constant, VT=kT/q); and a variable gain amplifier which receives and converts the output gain control signal VX output from the control signal converter so that the gain has a linear-in-dB characteristic. A shape of a gain curve is externally controlled.