Epitaxial wafer for heterojunction bipolar transistor, and heterojunction bipolar transistor

Provided are an epitaxial wafer for a heterojunction bipolar transistor in which the base resistance and the turn-on voltage can be reduced to a greater extent than in the past, and a heterojunction bipolar transistor. An epitaxial wafer (100) for a heterojunction bipolar transistor, the epitaxial wafer (100) being provided with: a collector layer (103) comprising GaAs; a base layer (second base layer (105)) formed on the collector layer (103), the second base layer (105) comprising InGaAs; and an emitter layer (106) formed on the second base layer (105), the emitter layer (106) comprising InGaP, wherein a base layer (first base layer (104)) comprising GaAs is inserted between the collector layer (103) and the second base layer (105).