To appropriately control pressure contact of grinding tools against the inner circumferential face of a hole to be worked at a final finishing work by measuring the changing rate of worked diameter per unit time, and controlling expansion pressure for honing based on the measured results.

When expansion pressure is reduced so as to execute a final finishing work, air is jetted from a sizing nozzle 13 to the inner circumferential face of a worked hole WH, back pressure at this time is detected by a A/E air-electric converter 15, and the changing rate of worked diameter per unit time is computed by a computation processing device 19. When this changing rate is larger than a set value, expansion pressure is reduced, in addition, the peripheral speed and the stroke speed of honing tools 1 are reduced, and hence the honing work is continued while the working condition is lowered so as to reduce a working quantity per unit time.