The present invention relates to a conjugate comprising oxyntomodulin, an immunoglobulin Fc region, and non-peptidyl polymer wherein the conjugate being obtainable by covalently linking oxyntomodulin to immunoglobulin Fc region via non-peptidyl polymer, and a pharmaceutical composition for the prevention or treatment of obesity comprising the conjugates. The conjugate comprising oxyntomodulin and the immunoglobulin Fc of the present invention reduces food intake, suppresses gastric emptying, and facilitates lipolysis without side-effects, unlike native oxyntomodulin, and also shows excellent receptor-activating effects and long-term sustainability, compared to native oxyntomodulin. Thus, it can be widely used in the treatment of obesity with safety and efficacy.
