A method of producing a photocatalyst according to the invention comprises forming an amorphous titanium oxide and heat-treating it in an atmosphere containing oxygen, whereby a photocatalyst having a good photocatalysis can be obtained. In particular, the amorphous titanium oxide is obtained by using the reactive sputtering method and via deposition at a low temperature and at a high film formation rate. This apparatus can be provided with cooling means to allow enhancement of the throughput of the film formation process.