Changes in the crystal structure and the lattice constants of powdered crystalline V2O5 after absorption of hydrogen were measured, as a function of the concentration, by X-ray diffractometry. The diffraction spectra obtained showed that three kinds of phases, alpha (x < 0.4 in HxV2O5), beta (co-existing with either terminal phase in the range of 0.4 less-than-or-equal-to x < 3.2) and gamma (3.2 less-than-or-equal-to x less-than-or-equal-to 3.9), appear up to x = 3.9, which was found to be the upper limit of the absorption at 70-degrees-C under a hydrogen pressure of 5 M Pa. The crystal system of the three phases was determined to be orthorhombic, although the lattice constants differed. The diffraction lines were broadened, and the background of the X-ray spectra grew with hydrogenation, especially in the gamma-region, which indicates the growth of the lattice distortion and a quasi-amorphous state. The occupation of hydrogen atoms in each phase is discussed on the basis of the experimental results.