The electronic states of Heusler (L2 1 )-type off-stoichiometric Fe 2-x V 1+x Al alloys have been investigated by soft x-ray angle-resolved photoelectron spectroscopy (ARPES) to clarify the origin of the remarkable increase in thermoelectric power, which cannot be explained by the rigid-band model. In off-normal and normal ARPES, Fe 2.05 V 0.95 Al shows weakly dispersive bulk bands from the binding energy of 0.3 eV at the Γ point in the Γ-X and Γ-L directions, and an almost dispersionless one around 0.3 eV in the gap of dispersive bulk bands in the Γ-L direction, which is attributed to antisite Fe defects. At the Γ point, the bulk bands do not appear to cross the Fermi level E F , which is consistent with the rigid-band model for excess Fe content, but no band crossing E F is found at the X point. The antisite Fe defect states near E F might push up the band at the X point and cause p-type thermoelectric properties, which is unexpected for the rigid-band model. The change in electronic structures and thermoelectric properties for the off-stoichiometry and substitution by a forth element is discussed.