To provide an adjustment clasp hook which is attached mainly to the waist part of trousers, a skirt and so on as waist size adjustment and is used, can adjust these sizes automatically within a certain definite range, and can be attached to and removed from a garment hook at the time of purchase.

The adjustment clasp hook includes an abutment piece to prevent the disengagement of a clasp hook main constituent by the energizing force of a spring, the bottom, a clasp hook base to form a sliding rail, a thrust piece to depress the spring, and a clasp piece which is formed with a gap. The clasp hook main constituent to slide by a rail covering edge which is a guide means for the sliding rail and the spring which is interposed in spring storage space between these are included. In an adjustment clasp hook which can adjust the waist size of a skirt, trousers, and so on automatically, the clasp piece provided on the clasp hook main constituent forms one or two or more female hooks. The adjustment clasp hook is characterized by providing the clasp hook base with a male hook.