The effect of the photodeposition of gold particles onto several photocatalysts on the photocatalytic activities was studied. The photocatalytic activities of K4Nb6O17, Sr2Nb2O7, KTaO3 NaTaO3, and NaTaO3 doped with La for water splitting were improved when gold particles were deposited. The latter were nanoparticles, consistent with their surface plasmon absorption. The nanosized gold particle functioned as an efficient cocatalyst for photocatalytic water splitting by assisting H-2 evolution.