The present invention relates to a polypentafluorophenyl ester-based polymer used in the manufacturing of an electrochemical sensor, wherein the polymer has high reactivity with an amine functional group, causes less hydrolysis, retains good solubility, for general purposes, in organic solvents, and has low steric hindrance and toxicity or side effects compared with polymers having a similar structure, and thus is useful in an insertion-type device, especially a continuous glucose monitoring system, a part of which is inserted into the human body.