Production lapping of lead zirconate-titanate ceramics are dealt with lapping rate, parallelism, yield and machining time including cutting-off time, since ceramics are machined as planeparallel, slender, thin plates in using for relay switches. The results obtained are as follows : (1) The order in lapping rate is A (no additive) >D (added Cr) >C (added Nb) >B (added Fe). Strong specimen C has a yield of 95%. (2) The difference in plate thickness within 10μ and the parallelism of 2μ are obtained from plane-parallel lapping, where the motion of specimens is restricted in carriers. (3) The concentration of lapping vehicle influences on lapping rate only by a factor of 5%. Supplying vehicle at a rate of 150 cc/min is desirable for preventing from breakage of plates. (4) Cut-off thickness is chosen as 0.3 mm regardless of the kind of ceramics. The whole machining time in lapping plates of 0.3 mm thick to 0.2 mm thick is shortened by a factor of about 40% than in lapping plates of 0.5 mm thick.