Hydrothermal treatment of an outer layer of a bark of Hinoki (Chamaecyparis obtusa) tree was investigated qualitatively for the possibility of utilizing residual forest biomass to produce valuable chemicals. Experiments were carried out in a semibatch reactor apparatus that allows the study of the effect of reaction temperatures in a single run. Gas chromatography-mass spectrometry analyses show the presence of useful chemicals such as furfural, aromatic compounds (1,3-di-tert-butyl benzene and 2,4-di-tert-butyl phenol), and fatty acids (myristic acid, palmitic acid, and stearic acid) in the products.