Abstract: A knife sharpener comprises an elongated blade holder with a clamping device for holding a blade at one end of the holder with the blade extending transversely the length of the holder, a post extending from the other end of the holder perpendicular to the plane in which the blade is gripped, and an elongated sharpening element having a sharpening surface extending over part of its length and a guide slot for receiving a ball at the top of the post extending along the remainder of its length. Engagement between the ball and the guide slot with the sharpening surface contacting an edge of the blade to be sharpened establishes the sharpening angle which is maintained throughout sharpening strokes of the sharpening element. The post may be adjustable in height to adjust the sharpening angle and may be replicated on opposite sides of the holder.