To obtain a photocatalyst sheet that can manifest excellent decomposi tion function to odorous substance and fouling substance as well as excellent post processability and flame retardancy and is useful as a filter for an air washer by using a photocatalyst, microbial cellulose and a carrier-forming component.

This photocatalyst comprises (A) a photocatalyst, (B) a microbial cellulose (for example, cellulosic substance produced by the spinner culture) and (C) a carrier-forming component. In an embodiment, the components A, B and C, when necessary, (D) a coagulant are used so that the rate of the amount of the component A (ZA) to the product of the photocatalyst retention index of the component B (XB), namely ZA/(XB×ZB) may become 0.5-2 and their mixture is made to paper according to the wet process.