The present invention provides an N1-2-thiophen-2-ylethyl-N2-substituted biguanide derivative of formula (I) or a pharmaceutically acceptable salt thereof, a method for preparing same, and a pharmaceutical composition comprising same as an active ingredient. The inventive N1-2-thiophen-2-ylethyl-N2-substituted biguanide derivative exhibits improved blood glucose level- and lipid level-lowering effects even with a reduced dosage as compared to conventional drugs, and thus, it is useful for preventing or treating diabetes, metabolic syndromes such as insulin-independent diabetes, obesity and atherosclerosis, or a P53 gene defect-related cancer.