The energy-band structures of the GaAs, GaP, and Ga As1-xPx alloys have been calculated on the "empty lattice" assumption by taking the pseudopotential as perturbations.The pseudopotential parameters are chosen so as to make the calculated direct and indirect energy gap agree with that given by the experiments. The results thus obtained are in good agreement with experimental data at room temperature. Assuming that the lattice constant and pseudopotential parameters vary linearly from GaAs to GaP, we have calculated the energy band of the GaAs1-xPx alloys for x=0.2, 0.5, and 0.8. The direct and indirect energy gap is equal at x=0.41 which is in reasonable agreement with the results of Spitzer and Fenner.