Abstract: Provided is a binder in which a binder is provided with a binding member having a pressing portion pressing a material to be bound, an operation member operated so as to pivotally rotate to an open state and a hold state, and a base member the binder is further provided with an engagement body, a projection portion caused to engage with the engagement body, and a supporting portion provided with the engagement body, the supporting portion is configured so as to bend toward the projection portion side and bend in a direction of separating from the projection portion and the locked state is formed by engagement between the engagement body and the projection portion.

Abstract: The present invention provides a binder where operations for locking and for unlocking are easily understood; and wherein a binder 20 is provided with a binding member 70 having a pressing portion 72 pressing a material to be bound, an operation member 60 operated so as to pivotally rotate to an open state and a hold state, and a base member 22 the binder 20 is further provided with an engagement body 120, a projection portion 100 caused to engage with the engagement body 120, and a supporting portion 180 provided with the engagement body 120, the supporting portion 180 is configured so as to bend toward the projection portion 100 side and bend in a direction of separating from the projection portion 100 and the locked state is formed by engagement between the engagement body 120 and the projection portion 100.