Abstract: An aspect of the present invention relates to a mask filter, wherein wet nonwoven fabric comprised of synthetic fiber is folded up into a concentric circular pleat form, and the synthetic fiber comprises 10 to 50 mass percent of short fiber A having a fiber length ranging from 0.1 to 1 mm and a fiber diameter ranging from 100 to 1,000 nm, and further comprises binder fiber B having a fiber length ranging from 5 to 10 mm and a fiber diameter ranging from 6 to 15 ?m, and fiber C of greater fiber length and fiber diameter than short fiber A and smaller fiber length and fiber diameter than binder fiber B.