A binding device comprising: a plurality of openable-closable binding rings (12, 14); a holding member having a length which allows the binding rings (12, 14) to be disposed with a spacing therebetween; an operating member having a surface to which base portions of the respective binding rings (12, 14) are secured such that the binding rings (12, 14) are disposed with a spacing therebetween, the operating member being movably secured inside the holding member such that the binding rings (12, 14) are secured to the holding member; and an opening-closing member which urges the binding rings (12, 14) in an opening direction, wherein: each of the binding rings (12, 14) includes a main binding ring which is directly closed with fingers and a subsidiary binding ring which follows the movement of the main binding ring in a closing direction of the main binding ring; and the main and subsidiary binding rings (12, 14) are configured such that, when the main and subsidiary binding rings (12, 14) are moved in the closing direction along an axial direction thereof, engaging portions on free ends thereof are engaged with each other at respective normal positions to close the binding rings (12, 14) and, when moved in the opening direction, the binding rings (12, 14) are opened; characterized in that the main and subsidiary binding rings (12, 14) are formed such that, when the main and subsidiary binding rings (12, 14) are closed, the engaging portions on the free ends of the main binding ring are moved in the closing direction past their normal position for engagement, while the engaging portions on the free ends of the subsidiary binding ring engage with each other at their normal position; and the operating member is provided with a movement restricting portion (30f, 30g, 32f, 32g) which, when the binding rings (12, 14) in an opened state are closed, restricts the distance of movement of the engaging portions of the free ends of the main binding ring in the closing direction past the normal position for engagement. a plurality of openable-closable binding rings (12, 14); a holding member having a length which allows the binding rings (12, 14) to be disposed with a spacing therebetween; an operating member having a surface to which base portions of the respective binding rings (12, 14) are secured such that the binding rings (12, 14) are disposed with a spacing therebetween, the operating member being movably secured inside the holding member such that the binding rings (12, 14) are secured to the holding member; and an opening-closing member which urges the binding rings (12, 14) in an opening direction, wherein: each of the binding rings (12, 14) includes a main binding ring which is directly closed with fingers and a subsidiary binding ring which follows the movement of the main binding ring in a closing direction of the main binding ring; and the main and subsidiary binding rings (12, 14) are configured such that, when the main and subsidiary binding rings (12, 14) are moved in the closing direction along an axial direction thereof, engaging portions on free ends thereof are engaged with each other at respective normal positions to close the binding rings (12, 14) and, when moved in the opening direction, the binding rings (12, 14) are opened; characterized in that the main and subsidiary binding rings (12, 14) are formed such that, when the main and subsidiary binding rings (12, 14) are closed, the engaging portions on the free ends of the main binding ring are moved in the closing direction past their normal position for engagement, while the engaging portions on the free ends of the subsidiary binding ring engage with each other at their normal position; and the operating member is provided with a movement restricting portion (30f, 30g, 32f, 32g) which, when the binding rings (12, 14) in an opened state are closed, restricts the distance of movement of the engaging portions of the free ends of the main binding ring in the closing direction past the normal position for engagement. each of the binding rings (12, 14) includes a main binding ring which is directly closed with fingers and a subsidiary binding ring which follows the movement of the main binding ring in a closing direction of the main binding ring; and the main and subsidiary binding rings (12, 14) are configured such that, when the main and subsidiary binding rings (12, 14) are moved in the closing direction along an axial direction thereof, engaging portions on free ends thereof are engaged with each other at respective normal positions to close the binding rings (12, 14) and, when moved in the opening direction, the binding rings (12, 14) are opened; characterized in that the main and subsidiary binding rings (12, 14) are formed such that, when the main and subsidiary binding rings (12, 14) are closed, the engaging portions on the free ends of the main binding ring are moved in the closing direction past their normal position for engagement, while the engaging portions on the free ends of the subsidiary binding ring engage with each other at their normal position; and the operating member is provided with a movement restricting portion (30f, 30g, 32f, 32g) which, when the binding rings (12, 14) in an opened state are closed, restricts the distance of movement of the engaging portions of the free ends of the main binding ring in the closing direction past the normal position for engagement.