To provide an edging device and its method for a blade with a curved blade line which can be automated.

An edging device is constituted of a grinder, a loading device, and a work moving device. The grinder is provided with a grinding face 88 of a sand belt 89 which is continuously traveling. The loading device applies a prescribed load on a section between a knife 6 and the grinding face 88 in their contacting direction in such a state that the longitudinal direction of the knife 6 having a curved edge line is positioned approximately crossing at right angle with the traveling direction of the grinding face and inclined to the grinding face 88 by an angle corresponding to a prescribed edging angle, so that the edge part 6d of the knife 6 and the grinding face 88 are brought in close contact. The work moving device makes the knife 6 move in the approximately the same direction as the longitudinal direction of the knife 6 in this state. The knife 6 thus automatically moves in the contact direction between the edge part 6d and the grinding face 88 so that the edge part 6d and the grinding face 88 are brought in contact all the time.