The present invention relates to a method for preparing an extract from the mycelial culture medium of Ceriporia lacerata and a pharmaceutical composition for preventing or treating diabetic diseases and diabetic complications prepared by the preparation method. According to the method for preparing an extract from the mycelial culture medium of Ceriporia lacerata, the extract contains a relatively high content of expolysaccharides in comparison with the conventional preparation method according to a prior document by these inventors and thus will be capable of being used as an ingredient for a pharmaceutical composition for diabetic diseases or a relevant functional food.
