A visible-light-responsive photocatalyst powder includes a tungsten oxide powder. When the tungsten oxide powder is measured by X-ray diffractometry, (1) among intensity ratios of a peak A (2θ=22.8 to 23.4°), a peak B (2θ=23.4 to 23.8°), a peak C (2θ=24.0 to 24.25°), and a peak D (2θ=24.25 to 24.5°), an A/D ratio and a B/D ratio each fall within a range of 0.5 to 2.0, and a C/D ratio falls within a range of 0.04 to 2.5, (2) an intensity ratio (E/F) of a peak E (2θ=33.85 to 34.05°) to a peak F (2θ=34.05 to 34.25°) falls within a range of 0.1 to 2.0, and (3) an intensity ratio (G/H) of a peak G (2θ=49.1 to 49.7°) to a peak H (2θ=49.7 to 50.3°) falls within a range of 0.04 to 2.0, and the tungsten oxide powder has a BET specific surface area in a range of 1.5 to 820 m2/g.