A bias circuit operable to supply a bias current to a first transistor includes: a second transistor having a collector terminal connected to a first power supply; a first resistance element having one end connected to an emitter terminal of the second transistor and having the other end connected to a base terminal of the first transistor; a second resistance element having one end connected to the emitter terminal of the second transistor and having the other end connected to ground potential; at least one third resistance element provided between a base terminal of the second transistor and a second power supply; and a plurality of temperature compensation circuits connected to the base terminal of the second transistor which are operable to control a base potential of the second transistor so that the potential falls as a temperature rises.