This study was carried out to investigate the physical and mechanical properties of 6 hardwoods before and after heat treatment in an effort to produce the high quality industrial lumber product. The results were as follows. Specific gravities of green woods were in range from 0.90 to 1.10. The specific gravities of never treated woods showed higher than those of the heat treated woods. The shrinkage of heat treated woods when green to air & oven dry was significantly low, compared to never treated woods. The compression strengths parallel to grain of heat treated woods showed higher than those of never treated woods. The moduli of rupture (MOR) of never treated and heat treated woods were $176.4N/mm^2{sim}102.8N/mm^2$ and $100.1N/mm^2{sim}61.2N/mm^2$ respectively. MORs of heat treated woods showed lower than those of never treated woods. There was no significant change in the modulus of elasticity (MOE) before and after heat treatment.