A single phase of Ca4Bi6O13 crystal was obtained at lower calcination temperature in a citric acid complex method than in a solid-state reaction. From the diffuse reflection spectra, it was found that Ca4Bi6O13 is direct-gap material and that the optical band gap is 2.92 eV. After heating at 600 degrees C or above, the specific surface area of Ca4Bi6O13 powder was ca. three times larger when prepared by a citric acid complex method than by solid-state reaction. Further, it was confirmed that the photocatalytic activity of Ca4Bi6O13 for the degradation of Methylene Blue (MB) was higher in a citric acid complex method than in a solid-state reaction under visible-light irradiation (lambda >= 420 nm).