An implant including a screw body composed of pure magnesium or a magnesium alloy and having a male thread, and the implant further including an anodized membrane covering an outer surface of the screw body. The male thread has a clearance flank and a pressure flank. The clearance flank faces forward in a traveling direction and the pressure flank faces rearward in the traveling direction during a screwing process of the screw body. The biodegradation period of the anodized membrane on the clearance flank is shorter than the biodegradation period of the anodized membrane on the pressure flank.