Binding-fastener fixing device, file, and binding-fastener fixing mechanism

A binding-fastener fixing device facilitates accurate positioning of a binding fastener when the fastener is fixed in position. The binding-fastener fixing device has a body section which is mounted to a file body, an inserting section which is inserted into a communicating hole formed by superposing a fixing hole section and a file-side hole section on each other, an engaging section which is provided to the inserting section and which, when the inserting section is inserted into the communicating hole, engages with and disengages from an engagement receiving member which is either the file body or a binding fastener which is located on the inner side, in the insertion direction, of the inserting section, and an inserting section-side fitting section which is provided along the directionof insertion of the inserting section into the communicating hole, with either the file body or the binding faster, which is located between the body section and the engagement receiving member, functioning as a member to be