The present invention relates to a medium composition for inducing the differentiation into insulin-producing cells, the composition containing glucosamine; a method for inducing the differentiation into insulin-producing cells by using the medium composition, and a cell therapeutic agent for treating diabetes, containing insulin-producing cells prepared by the method. The glucosamine according to the present invention can effectively induce the differentiation into insulin-producing cells through the regulation of sugar metabolism. The induction of the differentiation into insulin-producing cells using glucosamine as described above has advantages of being safe due to the exclusion of genetic manipulation; being performed at low cost since high-priced compounds or growth factors with unidentified mechanisms are not required; and minimizing cell contamination and deformation, which are caused at the time of ex vivo manipulation, due to the induction in a short period of time.