To provide a binder for a document having high safety for effectively satisfactorily locking.

The binder for a document comprises through holes 4a, 4b provided at both ends of both bouncing plates 2a, 2b, an opening 7 provided between both the plates 2a, 2b at both ends of both the plates 2a, 2b, a protruding engaging part 10 having a gate-like section opened at a lower part of a direction perpendicular to a longitudinal direction of a frame 1, and protrusions 6a, 6b engaged with the through holes from above at both ends extended to both sides from an arm 5b formed at an end of a neck 5a bent from a lower end of one operating lever 5. An upward protrusion 9 to be engaged with the protruding engaging part of the frame at the final time of erecting the lever 5 is formed at a center of an upper edge of the arm 5b, and the lever 5 formed with a lower leg 5c of an inverted T state to be engaged within the opening is tiltably mounted at both end sides of the frame from below the center of the arm 5b.