The present invention relates to a sexual function improving composition containing as an active ingredient: exopolysaccharide produced by means of Ceriporia lacerata; a Ceriporia lacerata mycelium culture medium comprising the exopolysaccharide; dry powder of the mycelium culture medium; or an extract of the mycelium culture medium. The composition can be used as a sexual function improving drug for preventing or treating erectile dysfunction or diabetic erectile dysfunction or as a functional health food having sexual function improving effect.