AbstractThis study investigated the application of heat to wood samples from Japanese cedar trees (Cryptomeria japonica) of small and medium diameters to evaluate the effects of both the temperature and duration of treatment on its surface, physical, and mechanical properties. The results indicate that the density, moisture content, and hygroscopicity of the wood samples decreased as the treatment temperature and duration increased, and the mass loss increased under the same conditions. Additionally, the dimensional stability of the wood improved in response to increased temperatures and prolonged durations. These results suggest that heat treatment can be used to improve the dimensional stability of wood. The surface color of the wood darkened progressively with increasing treatment temperature and duration, and the hydrophobicity of the wood sample improved as a result of the heat treatment. In contrast to the untreated wood, the heat-treated wood exhibited decreased mechanical properties with an increase in the treatment temperature and duration.