PURPOSE: To precisely measure the machined diameter of the bore of a workpiece so as to improve honing accuracy. CONSTITUTION: A honing head 11 is provided in such a way as to be rotatable and axially reciprocated, and a head rotating device 17 is provided to rotate the honing head 11. The honing head 11 is provided with plural honing sticks 33 spaced appropriately in the circumferential direction and movable in the radial direction, and a honing stick operating device 47 is provided to move plural honing sticks 33 synchronously outward in the radial direction. A control device is provided to control the head rotating device 17 so as to slow down the rotating speed of the honing head 11 almost simultaneously with starting to measure the machined diameter of a bore H, and to control a coolant feeder 73 so as to reduce the supply quantity of a coolant while maintaining the required minimum supply quantity of the coolant.