There is provided a filter element which maintains the flow rate of a fluid passing through a filter medium, restrains a pressure loss as far as possible, and is compact in size. In the filter element including a filter medium 30 pleated so that peaks 30a and valleys 30b are arranged alternately and a frame 21 for holding the filter medium 30, the frame 21 includes a frame body 22 forming the peripheral edge portion thereof and a plurality of ribs 23 extending in parallel on the inside of the frame body 22. The interval H between the ribs 23 is set at 5 to 35 mm, and the filter medium 30 is folded at an angle θ of at least four degrees at the peaks 30a and the valleys 30b.