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.