The purpose of the study is to propose new abrasive machining under wet condition and constant pressure by using chaos, Rotation of an abrasive motor is statically controlled to become chaotic. The following facts are revealed by experiments : (1) A period 1.06 s of a chaotic rotational change is superior than other periods in removed volume and abrasive efficiency. (2) Chaotic rotation of a period 1.06 s is twice as good as maximum and constant 12000 rpm in abrasive efficiency. (3) A chaotic rotational change is superior than changes generated by a sine wave or a random signal in both of removed volume and abrasive efficiency. (4) Reduced percentage of final surface roughness is 96.5-99.5%, when a plane (Ra 2. 3-2. 7μm) machined by WEDM is selected as a target. (5) Rotational change is not so serious that the influence in surface roughness is within 0.1-0.2μm (P-V). (6) The best surface roughness is determined by size of grains and is 50-100 nm (P-V), when #120 grains are used under wet condition and constant pressure.