An epitaxial wafer for a heterojunction bipolar transistor and a heterojunction bipolar transistor capable of reducing the resistance of the sub-collector layer without reducing the current amplification factor are provided. In an epitaxial wafer for a heterojunction bipolar transistor including a sub-collector layer made of n-type GaAs, the sub-collector layer contains n-type impurities having a covalent radius that is smaller than the covalent radius of the substitution site and n-type impurities having a covalent radius that is larger than the covalent radius of the substitution site.