Disclosed is a diffuser tube which is capable of preventing the blockage of diffusion holes and the inside of the tube by preventing the entry of sludge into the tube during the stoppage of air diffusion, and also capable of reducing a pressure loss during a diffusion operation. Specifically disclosed is a diffuser tube which is composed of a tubular elastic body and wherein in a tilted surface section (55) of each slit, the cut surface of the slit is tilted with respect to the radial direction of a film (52).