Decay behavior of photostimulated exoelectron emission (PSEE) from aluminumsurface after abrasion was examined under air and argon in a gas-tightchamber. Detection of PSEE was conducted by picoammeter under irradiationof an ultraviolet light. Wavelength of the light was controlled by a UV-filter.Effects of water and oxygen on the decay behavior were tested. Water and oxygenin argon were removed by a liquid oxygen trap and a furnace with titanium tips, respectively. Oxygen partial pressure was monitored continuously by a solid stateelectrolyte of zirconia. Decay process of PSEE under atmospheric pressure wasnot expressed by a simple kinetic equation. Although oxygen, impurity in argon, did not affect the decay behavior, water in air and argon promoted decay of PSEEleaving irreversible change on aluminum surface.