PROBLEM TO BE SOLVED: To provide a pharmaceutical composition for the prevention or treatment of diabetic diseases and diabetic complications.SOLUTION: Provided are: a preparation method of an extract of Ceriporia-lacerata mycelium culture liquid a pharmaceutical composition containing a purified extracellular polysaccharide for preventing or treating diabetic complications prepared by said preparation method according to the preparation method of an extract of Ceriporia-Lacerata mycelium culture liquid, the extracellular polysaccharide is contained at a higher content in the extract as compared with the conventional preparation method, thereby a purified bacterial extracellular polysaccharide which can be applied as a pharmaceutical composition for diabetic diseases or as a material for related functional food products and a purified extracellular polysaccharide having a molecular weight of about 120 kDa and containing sugar by about 40 wt.% and protein by about 33 wt.%.SELECTED DRAWING: Figure 19