To provide an air cleaner in which air flows smoothly.

This air cleaner 72 comprises a suction port 74a for introducing the outside air, a discharge port 73a formed on the opposite side of the suction port, and a filter 75. The filter 75 is so disposed as to extend from the suction port side to the discharge port side. The side wall part 74b of a case cover 74 forming a suction side air chamber S1 is so formed that its distance from the filter is reduced from the suction port toward the bottom of the suction side air chamber. The side wall part 73b of the case body 73 forming an exhaust side air chamber S2 is so formed that its distance from the filter is increased toward the discharge port.