Abstract: A truing device that can form surfaces of hones, installed in a honing tool, into R-shapes (i.e. provided with rounded off edges or corners) with the same diameter as that of the honing tool or plane shapes. A truing tool is provided with a penetrating hole through which the honing tool is inserted and at least a part of an inner surface of the penetrating hole is a cylindrical surface having the same diameter as that of the honing tool and at least a part of said penetrating hole inner surface is provided with cutting edges for hone grinding. A tool holder housing the truing tool attachably and removably is held in a jig body of a tool holding device in a manner that the tool holder can shake within a range of three dimensional minute angles, thereby allowing said truing tool to smoothly follow movement of said honing tool during truing.