The influence of density and water content of wooden biomass briquette on the thermal diffusivity is investigated. The temperatures of three position inside the cylindrical briquette are measured by using sheath K-type thermocouple and the difference equation derived from one-dimensional heat equation is used to estimate the thermal diffusivity. In low water content briquette, the thermal diffusivity with high density (1300kg/m^3) is slightly greater than that with low density (800 kg/m^3). In high density briquette (1300kg/m^3), there is a tendency that the thermal diffusivity with high water content (10.8%) is greater than that with low water content (2.3%) after drying.