To provide a filter unit hardly causing the deformation of a filter medium even when the height of the filter unit in the direction of a pleating line exceeds 610 mm and the pressure loss is increased, and having excellent maintainability and to provide a unit-exchangeable filter system.

This filter unit 113 is housed to be attached/detached to/from a frame 112 of the unit-exchangeable filter system. The unit 113 consists of a layered body obtained by layering at least two pleated filter media 115 in the direction of the pleating line and integrating the end faces 115a, which are superimposed on one another in the direction of the pleating line, of the media 115 with one another while interposing a reinforcing plate 117. One piece 112a parted from the frame 112 is joined to the side face of the layered body or the end face of the layered body in the media 115-layered direction. When the unit 113 is housed in the frame 112, the piece 112a is integrated with the frame 112.