To obtain a composition for forming a transparent photocatalyst layer, which can form the transparent photocatalyst layer exhibiting photocatalytic activity even in an indoor environment.

This composition for forming the transparent photocatalyst layer contains titanium dioxide as a photocatalyst. The titanium dioxide to be used is composed of anatase type titanium dioxide having larger particle size and rutile type titanium dioxide having smaller particle size and has 5-100 nm average particle size. The ratio of the average particle size of the anatase type titanium dioxide to that of the rutile type titanium dioxide is 4:1 to 20:1 and the weight ratio of the anatase type titanium dioxide content to the rutile type titanium dioxide content is 2:1 to 10:1.