To provide an air purifier, effectively using incident light and efficiently perform decomposition of harmful component and malodor component using photocatalytic action substance.

This air purifier is formed by stacking a reflector reflecting light on the bottom of a sponge-like sheet carrying photocatalytic action substance on the surface and in the interior thereof. The air purifier is formed by storing the sponge-like sheet carrying the photocatalytic action substance on the surface and in the interior thereof in a container, the top surface of which is opened. In the air purifier, the reflector is stored at least at the bottom of the container or the inner wall surface of the bottom of the container is formed by the reflector.