The bulk and surface electronic structures of Sm4As3 have been investigated by hard and soft X-ray photoemission spectroscopies (PESs). PES with a wide range of photon energies (h nu's) between 220 and 2450 eV demonstrates the absence of valence mixing in both high- and low-temperature phases, that is, the valence of Sm ions is definitely trivalent in the bulk and divalent on the surface. Atomic multiplet calculations taking into account the bulk and surface spectral weights at each hnu well reproduce the experimental valence band PES and Sm 3d core-level spectra, supporting the valence difference between bulk and surface in Sm4As3.