Measurements of the mass distribution of xenon clusters in a pulsed supersonic beam during ionization by electrons and photons are carried out. For ionization by electron impact, an electron gun was used. The energy of the electron beam varied in the range 15 - 70 eV. Third harmonic of a titanium-sapphire femtosecond laser with a wavelength of 263 nm was used for multiphoton optical ionization. Clusters of xenon Xe_N with N < 1000 were observed in a supersonic beam,. It is shown that the shape of the mass spectrum in multiphoton optical and electronic ionizations coincide at the electron energy near the ionization threshold (15 - 20 eV). At the electron energy of 30 - 70 eV the shape of the mass spectrum is substantially distorted in the region N ∼ 2 - 150. The change in the shape of the mass spectrum is mainly due to the large fragmentation of multiply ionized xenon clusters due to Coulomb decay.