An air cleaner is provided with a housing having an opening, and a filter. The filter has a frame and an element supported to the frame. The filter is installed in the interior of the housing from the opening of the housing. A second seal surface of a seal ring of the filter is joined to a first seal surface of the housing in a state in which the filter is installed in the housing. A rib-shaped protection portion extending along the first seal surface is provided in the housing. The protection portion protrudes further toward the filter than the first seal surface. A slide protrusion protruding further toward the first seal surface than the second seal surface is provided in the frame of the filter. The slide protrusion can slide on the protection portion.