The paper deals with machinability of boron nitride (BN) added steels. BN has hexagonal system, and the nature is similar to graphite so that it is used for solid lubricant in general. In this study, plain carbon steel S45C and BN added steels, which has also 0.45% carbon content, were machined by P grade and K grade carbide tools and an alumina ceramic tool. In turning the BN added steels, P grade tool had fairly smaller flank wear than that in turning 545C at the cutting speed of over 200 m/min and the effects of the good machinability kept even at the cutting speed of 500 m/min. At the lower cutting speed, however, the wears in turning the BN steel and 545C were almost the same. Furthermore, in the case of K grade carbide tool, the wear in turning the BN steel is almost the same as that in turning the S45C even at higher cutting speed, and the ceramic tool showed the same results as K grade tool.