The molecular beam epitaxy phase diagrams for the GaAs(001) surface have been determined using the reflection high-energy electron diffraction technique. The surface reconstructions were investigated during the growth processes carried out with a Riber 32P machine. In the experiments the substrate temperature, the Ga flux, and the As-4 flux were measured directly (the absolute values of the Ga and As-4 fluxes are given in the phase diagrams), The investigations of surface reconstructions were carried out for three different values of the Ga flux. During the growth processes the reconstructions (4X2), (3X1), (4X6), (3X6), (2X4), and (2X2) were observed. The boundaries between different reconstructions have been determined precisely for each value of the growth rate. The dependence of the positions of the boundaries on the Ga flux has been discussed. The obtained results have been compared with those known in the literature.