Mechanical properties in the radial direction of wood with different swelling ratio swollen in different organic liquids diluted with benzene were studied and compared with those swollen by moisture or water. Additionally, modulus of elasticity in bending of untreated or lignin extracted specimens were measured in the condition swollen by water or dimethyl sulfoxide. And, it was considered how the liquids were present in wood and affect mechanical properties. The modulus of elasticity and rupture in bending of specimens swollen by organic liquids diluted with benzene were decreased with increase in cross sectional relative swelling, and those values were larger than those of specimens swollen by moisture and water in similar degree of cross sectional swelling. This is attributed to the difference in the number of several hydrogen bonds between molecules of wood constituents, and the number is affected by the molecular size of the liquid. The degree of decrease in modulus of elasticity was smaller in the lignin extracted specimen due to change of liquids from water to dimethyl sulfoxide. This is because the lignin extracted specimen has few lignin, therefore, the specimen was not much swollen by dimethyl sulfoxide and mechanical property was also not largely decreased. From the results, it is clarified that dimethyl sulfoxide is adsorbed in lignin, and decrease in mechanical property is caused by swelling of lignin due to adsorption of dimethyl sulfoxide.