We have newly developed a semi-implantable and flexible electrochemical biosensor for detection of free cholesterol by electroplating Pt black on a micro-fabricated needle, which was made of a medical-grade thin stainless steel substrate with a thickness of 200 μm. The proposed free cholesterol sensor was comprised of two vertically stacked micro-needles with three electrodes, working (Pt black), counter (Pt black), and reference (Ag/AgCl) electrodes. The as-fabricated micro-needles-based biosensor was designed to have enough flexibility to be inserted into the human body. The electroplated Pt black showed a roughness factor of 444 and excellent catalytic activity. The fabricated biosensor showed a sensitivity of 0.625 mA/mM · mm2 using the amperometric measurement technique.