This study deals with shear strength test for Pinus densiflora and Pinus radiata treated at above $100^{circ}C$ by heat steam. Treatment conditions of this experiment were operated at regular intervals of $20^{circ}C$ at temperatures up to $200^{circ}C$ for 5, 10, 20 and 30 minutes by using the steam-explosion apparatus. It was examined, at high temperatures, degradation of some compounds from wood composition could lead to reduced the shear strength through heat steaming processes and play a large part in the plastic process of solid wood materials. It could be estimated that the shear strength of woods were gradually reduced by heat steaming time. Remarkable reduction of shear strength of woods was observed with increasing steaming temperatures above 10 minutes steaming time. Furthermore, this phenomenon shows a tendency to increase with higher temperatures. Therefore, it was considered that the softening by steaming treatment at high temperatures is necessary for the improvement on the wood processing ability.