PROBLEM TO BE SOLVED: To provide a pleated air filter which is easily pleated and has excellent air permeability.SOLUTION: There is provided the pleated air filter comprising at least two layers, wherein the one layer includes a mesh-like reinforcing net, and wherein a relationship of pleat crest height H (mm), pleat width W (mm) and length L (mm) of crease of the creased pleat to tanθ obtained from a tilting angle θ of weft of the reinforcing net in relation to the TD direction satisfies L/W
