To provide a novel visible light-responsive photocatalyst or tungsten oxide visible light-responsive semiconductor improved in environmental resistance under an alkaline condition. The tungsten oxide visible light-responsive semiconductor unstable under an alkaline condition is improved in environmental resistance without losing photocatalytic function thereof by adding thereto at least one element selected from the group consisting of copper, tantalum, niobium, lanthanum, bismuth, calcium, chromium, manganese and zinc. The obtained environmental resistant visible light-responsive photocatalyst is subjected to an alkaline treatment to thereby be improved in photocatalytic activity.