Abstract: Disclosed is an air filter using high density filter paper. The filter paper may include a thermally bonded non-woven fabric filter paper 10 having air permeability to filter foreign materials of passed polluted air and change the polluted air to fresh air. The non-woven fabric filter paper includes wrinkled portions 10-1 and 10-N that are folded at a predetermined interval. A thickness of the wrinkle portions 10-1 and 10-N are provided with dense layers 15 and 17 comprising a first polyethylene terephthalate (PET) fiber 20-2 that can shrink by heat and a second polyethylene terephthalate (PET) fiber 20-1 that deforms upon by heat treatment.