Effect of the thickness of packaging film on the ripening of mature-green mume (Prunus mume Sieb. et Zucc) fruit was investigated by measuring physicochemical changes of the fruit during storage. Fruits were packaged using low density polyethylene (LDPE) films with thicknesses of 20, 30, and 40$mu$m and stored at the room temperature. The physicochemical properties such as contents of various pectic substances, molecular weight distribution of soluble pectic substances, and surface image of the fruit were determined during storage of 8 days. In general, regardless of the thickness of the films applied, a content of water-soluble pectin (WSP) in the fruit was increased during storage, but both contents of HCI- soluble pectin (HSP), and Ca and Mg in total alcohol-insoluble solids were decreased. Sephacryl S-300 gel filtration study revealed that fractions of high molecular weight HSP and WSP decomposed into lower molecular weight pectins during storage. The scanning electronic microscope also identified a significant structural change of the fruit skin over the storage time. It could be concluded from the results that fruits packaged with LDPE 30${mu}{ extrm}{m}$ film maintained the highest physicochemical quality of green mume fruit during storage.