To provide a photocatalyst tube for effectively using a photocatalyst such as titanium oxide, and an air cleaner system using the photocatalyst tube.

Fine thread-like fibers of a unit of several tens micron are woven into a mat shape to form a coarse net thin plate by using glass fibers, and the thin plate thus prepared is machined into a tube, and a photocatalyst is fixed. Several photocatalyst tubes are bundled and arranged in a transparent glass container. An ultraviolet generating device is installed, and air or the like is caused to flow by a fan or the like in using the photocatalyst tube.