Abstract: A device for sharpening chain saw cutter teeth includes a rigid disc member which has an abrasive coating deposited on its outer circumferential edge. The abrasive coating has a circumferential outer grinding surface which, when viewed in cross-section on a plane which is perpendicular to and radial to the disc member, has a curvature which is adapted to conform to the curvature of a concave surface in a common type of chain saw cutter tooth. The device can be mounted to a common rotary tool such as a bench grinder or a portable grinder to manually sharpen a chain saw in an inexpensive and efficient manner.