To provide a remaining ring material cut-off implement for a cap receiving part of an opened PET bottle easily usable by a housewife or a child, and easily manufacturable and reducible in manufacturing cost by simplifying structure.

This cut-off implement is constituted such that an insert-through part 2 insertable through a clearance between the PET bottle and a remaining ring material left at the cap receiving part of the opened PET bottle by twisting a cap is formed at the tip part of a handle lever body 1 and that a cutting-off edge part 4 capable of cutting off the remaining ring material in a state of the insert-through part being inserted through the clearance between the PET bottle and the remaining ring material is formed at the side edge of the insert-through part.