Bi2MNbO7 (M=Al3+, Ga3+, In3+) solid photocatalysts were prepared by solid-state reaction and characterized by powder X-ray diffraction and Rietveld structure refinement. These photocatalysts crystallize in the same pyrochlore structure, but the lattice parameters decrease with decrease of M3+ (M3+=Al3+, Ga3+, In3+) ionic radii. The band gaps of Bi2MNbO7 (M=Al3+; Ga3+; In3+) were estimated to be about 2.9, 2.75 and 2.7 eV, respectively. The difference in the band gaps of the photocatalysts is due to their different conduction band levels, resulting in the difference in photocatalytic activity of the photocatalysts.