A benzofuran substance was isolated from the methanol extract of Pauownia tomentosa stem which has been used to treat against gonorrhoea and contusion etc. in the oriental traditional medicine. Its structure was elucidated as methyl-5-hydroxy-[1, 4]naphthoquino-[2, 3-b]benzo-[I, 2-g] benzofuran-6-carboxylate by X-ray crystallography and various spectroscopic evidences and also other three known compounds, paulownin, sesamin, $eta$-sitosteryl-3-O-$eta$-D-glucopyranoside, were obtained.