A bipolar transistor includes: a substrate; a collector and a base layer with a p-conductive-type, an emitter layer with an n-conductive-type. The collector layer is formed above the substrate and includes a first nitride semiconductor. The base layer with the p-conductive-type is formed on the collector layer and includes a second nit ride semiconductor. The emitter layer with the n-conductive-type is formed on the base layer and includes a third nitride semiconductor. The collector layer, the base layer and the emitter layer are formed so that crystal growing directions with respect to a surface of the substrate are in parallel to a [0001] direction of the substrate. The first nitride semiconductor includes: InycAlxcGa1-xc-ycN (0≦xc≦1, 0≦yc≦1, 0