The present invention relates to a composition for treating obesity-related diseases comprising an insulinotropic peptide conjugate, more particularly, to a composition for treating obesity-related diseases comprising a conjugate prepared by covalently linking the insulinotropic peptide with a carrier substance via a non-peptidyl linker, and a method for treating obesity-related diseases by using the same. In particular, the composition for treating obesity-related diseases according to the present invention remarkably improves the efficacy of suppressing food intake and its duration to reduce body weight and body fat, thereby being useful for the treatment of obesity-related diseases.