The present invention provides an air cleaner, in which a casing has an air inlet pipe making air inflow along a direction perpendicular to the axis of a cylindrical filter element, and an air outlet pipe making filtered air outflow along the axis, and the casing has a supporter clingingly supporting the end outer circumference of the filter element on closed valley portions side along the circumference direction continuously, and another supporter supporting the end inner circumference of the filter element on closed mountain portions side along the circumference direction continuously to close a hollow portion, and air to be filtered inflows to the filter element from a first inflow space on the top side of the mountain portions as well as from the end of a second inflow space side, and filtered air outflows from the end on an outflow space side as well as from the hollow portion.