Disclosed herein is a light-responsive photocatalyst composition, which is a composite oxide semiconductor containing tungsten, and which can efficiently absorb visible light emitted from the sun and light emitted from interior lamps, such as fluorescent lamps, etc., and a method of preparing the light-responsive photocatalyst composition. The visible light-responsive photocatalyst composition can decompose volatile organic compounds or harmful organic matter causing sick house syndrome, even indoors, because it can be activated by visible light outdoors and can respond to light emitted from interior lamps, such as fluorescent lamps, etc.