An electric nail filing device includes a cylindrical body having a battery holder attached inside in the body, a cover attached to an open end of the cylindrical body, an on/off switch attached on the cover or the cylindrical body, an electric motor having a metallic rotary filing wheel, and a safety guard cap attached and covering the wheel, shaped like a rectangular prism, a pentagonal prism, a hexagonal prism, or a multiplane prism having multiple planes and a tubular cylindrical housing inner space which has enough space to cover the wheel, in which the safety guard cap has multiple slots on the planes, and an adjustable guard tab attached at closed end of the safety guard cap. Optionally the safety guard cap is covered by a nail debris collector which is shaped like a half-dome covering all other planes of the safety guard cap except one plane.