An imaging lens and a projection device including the imaging lens are provided. The imaging lens includes a central lens portion and a peripheral lens portion arranged around the central lens portion. The peripheral lens portion has opposite first outer and inner surfaces, at least one of the first outer and inner surfaces has a plurality of first convex regions. The central lens portion has opposite second outer and inner surfaces, and at least one of the second outer and inner surfaces of the central lens portion protrudes beyond the corresponding first outer or inner surface of the peripheral lens portion.