Influence of boron and nitrogen addition as one of the alloying element on the formation of solidification structure and the improvement of hardness after thermal treatments was investigated for high-speed-steel alloys (Fe-2%C-5%Cr-5%Mo-5%V). The macrohardness of the quenched specimens gradually increases with increasing quenching temperature. Nitrogen addition helps to improve the hardness as carbon does. Boron addition is also contributed to the increasing of hardness. B-containing specimens maintained higher tempered-hardness than HSS and N-containing specimens quenched at the peak hardness. The specimen, which contains high volume fraction of residual austenite, shows the superior secondary hardening after the optimized tempering.