Si-doped titanias with a Si/Ti charged ratio of 0.2 was prepared by thermal reactions of titanium tetraisopropoxide and tetraethyl orthosilicate in 1,4-butanediol at 300 degrees C (glycothermal reaction) and N- and Si- co-doped titanias were prepared by heating the thus-obtained Si-doped titanias in an NH3 flow. N- and Si- co-doped titanias had a stronger absorption in a visible light region of 400-550 nm, and exhibited high photocatalytic activities for decomposition of acetaldehyde under visible-light irradiation. In this study, N- and Si-co-doped titanias were further modified with vanadium by an impregnation method using an ammonium vanadate solution, and the obtained catalysts were characterized by XRD, BET surface area measurement, UV-vis, and ESR. Photocatalytic decomposition of acetaldehyde using the V-loaded N- and Si- co-doped titanias was examined and it was demonstrated that a very small amount of V-loading (V/Ti = 0.0001-0.001) significantly enhanced the photocatalytic activity under visible-light irradiation.