To provide a carton cutter for recycling used drink cartons.

This carton cutter, with its body being held in one hand, is designed to cut a cornered edge of a box carton with a pull along the edge in a slight contact in a sliding manner after inserting the cutter's blade tip in the opening of the carton. The blade, which is gently curved like a fishhook, includes an inner edge to cut along the edge of the carton, and a spherical body fixed at the tip of the blade. The spherical body helps keep the blade from coming out of the carton or hold it inside when the body is being pulled, or even if too much pulling power is applied to force the blade happens to come out, the spherical body prevents it from injuring a user. The cutter body near the blade is scraped off to be rounded, so that it can easily be turned in a different direction to keep cutting without being taken out after finishing cutting the first side.