New solid solutions with the composition of Ca1-xBixVxMo1-xO4 prepared by a solid-state method were found as novel photocatalysts with enhanced activity for O-2 evolution from aqueous solutions containing sacrificial regent AgNO3 under visible-light irradiation (>420 nm). The obtained solid solutions crystallized in tetragonal crystal structures, except one of the end compounds, BiVO4, which crystallized in monoclinic structures. The diffuse reflection spectra of the solid solutions shift monotonically to a long wavelength as the ratio of Bi (V) ions to Ca(Mo) ions increases in the solid solution. The band structure and the dependence of the photocatalytic properties were discussed in relation to the solid-solution compositions and photophysical properties.