Fly cutting technique can perform low depth of cut machining which realize ductile mode cutting on hard brittle materials. Ultrasonically assisted machining can extend "critical depth of cut" which is maximum depth of cut to obtain ductile mode machined surface. Proposed technique which combined above two techniques employed to machine fine ceramics. Diamond sintered tools were used in these experiments. Machined surface by ultrasonically assisted fly cutting is smooth compared with ordinary fly cutting. Ultrasonically assisted fly cutting can perform ductile mode cutting of ceramics and is effective to machine hard brittle materials without brittle fractures.