the present invention relates to a biochip comprising an electrode having a titania coating layer on its surface ; an organic coupler comprising two or more carboxylic acid groups and capable of transporting electrons ; and bioactive molecules , wherein the organic coupler is covalently bonded to a hydroxyl group of titania on the electrode surface through one carboxylic acid group , and to the bioactive molecules through other one or more carboxylic acid groups , a method for analyzing target molecules using the biochip , a method for diagnosing the development of diseases using the biochip , an electrode provided with a titania coating layer on its surface to which an organic coupler , comprising 2 or more carboxylic acid groups and capable of transporting electrons , is bound , wherein the organic coupler is covalently bonded to a hydroxyl group of titania on the electrode surface through one carboxylic acid group , and a method for preparing the electrode provided with a mesoporous titania coating layer , the method comprising coating a mixed solution of a titania precursor and a template polymer on the top of the electrode , and calcinating the coated electrode under an air flow condition .