The effects of the surface oxidation on the helium desorption and retention behaviors of vanadium alloy were investigated. V–4Cr–4Ti alloy, which was thermally oxidized at 873K for 15min with 0.05Pa, was irradiated by helium ions with energy of 5keV at room temperature. Then, the helium desorption and retention behaviors were evaluated using a technique of thermal desorption spectroscopy. The changes in surface structures by the irradiation were also evaluated. Helium desorption behavior in low temperature region were significantly changed by the oxidation. Helium desorption around 700K became large for the oxidized sample. The amount of retained helium and the blister size in the oxidized sample were smaller than of those in the non-oxidized one. These results indicate that the surface oxidation significantly affects the helium retention and desorption behaviors of the vanadium alloy.