The dielectric relaxation due to motions of water molecules adsorbed on wood treated at various temperatures up to 550 degrees C was investigated based on the relationships between activation enthalpy (Delta H) and entropy (Delta S) in relaxation. The relationships indicated two straight lines with different slopes, depending on the treatment temperature. Given the same Delta S, Delta H values for water molecules adsorbed on wood treated at temperatures below 400 degrees C were greater than for those treated above 450 degrees C. It was considered that before heat treatment, water molecules were adsorbed mainly on hydroxyl groups by strong hydrogen bonds and formed ice-like structures. On the other hand, hydroxyl groups were not detected in wood after heat treatments above 400 degrees C. We assume that water molecules are condensed in nanometer-scale micropores that are formed during the carbonization of wood. The relationship between Delta H and Delta S for the motion of water adsorbed on wood treated above 450 degrees C was similar to the value extrapolated from that for bulk water at temperatures below 0 degrees C. We suggest that water molecules are adsorbed on charcoal in a supercooled state.