An epitaxial wafer for a light emitting diode, including a GaAs substrate, a light emitting unit provided on the GaAs substrate, and a strain adjustment layer provided on the light emitting unit, wherein the light emitting unit has a strained light emitting layer having a composition formula of (AlXGa1-X)YIn1-YP (wherein X and Y are numerical values that satisfy 0≦X≦0.1 and 0.39≦Y≦0.45 respectively), and the strain adjustment layer is transparent to the emission wavelength and has a lattice constant that is smaller than the lattice constant of the GaAs substrate. The invention provides an epitaxial wafer that enables mass production of a high-output and/or high-efficiency LED having an emission wavelength of not less than 655 nm.