A binocular system comprising: monoculars (10, 20) in pairs; and a coupling portion coupling the monoculars in pairs, wherein: one monocular has a connecting portion on a side of an objective lens thereof; the other monocular has a connected portion connectable to the connecting portion on a side of an eye lens thereof; the coupling portion includes a first coupling portion formed integrally with the one monocular, a second coupling portion formed integrally with the other monocular, and a hinge portion coupling the first coupling portion and the second coupling portion in such a manner that a mutual bending angle therebetween is adjustable centering around a bending axis; the one monocular and the other monocular are detachable from each other; the hinge portion has at least one shaft member movable forward and backward in a direction of the bending axis; one of the first coupling portion and the second coupling portion has the at least one shaft member; the other one of the first coupling portion and the second coupling portion has at least one engaged portion which is a recess engageable with the at least one shaft member; characterized in that the at least one shaft member comprises: either a ball engageable with the at least one engaged portion or a piston provided with a pin engageable with the at least one engaged portion at one end of the piston; and at least one elastic body energizing the ball or the piston toward the at least one engaged portion in the direction of the bending axis. monoculars (10, 20) in pairs; and a coupling portion coupling the monoculars in pairs, wherein: one monocular has a connecting portion on a side of an objective lens thereof; the other monocular has a connected portion connectable to the connecting portion on a side of an eye lens thereof; the coupling portion includes a first coupling portion formed integrally with the one monocular, a second coupling portion formed integrally with the other monocular, and a hinge portion coupling the first coupling portion and the second coupling portion in such a manner that a mutual bending angle therebetween is adjustable centering around a bending axis; the one monocular and the other monocular are detachable from each other; the hinge portion has at least one shaft member movable forward and backward in a direction of the bending axis; one of the first coupling portion and the second coupling portion has the at least one shaft member; the other one of the first coupling portion and the second coupling portion has at least one engaged portion which is a recess engageable with the at least one shaft member; characterized in that the at least one shaft member comprises: either a ball engageable with the at least one engaged portion or a piston provided with a pin engageable with the at least one engaged portion at one end of the piston; and at least one elastic body energizing the ball or the piston toward the at least one engaged portion in the direction of the bending axis. one monocular has a connecting portion on a side of an objective lens thereof; the other monocular has a connected portion connectable to the connecting portion on a side of an eye lens thereof; the coupling portion includes a first coupling portion formed integrally with the one monocular, a second coupling portion formed integrally with the other monocular, and a hinge portion coupling the first coupling portion and the second coupling portion in such a manner that a mutual bending angle therebetween is adjustable centering around a bending axis; the one monocular and the other monocular are detachable from each other; the hinge portion has at least one shaft member movable forward and backward in a direction of the bending axis; one of the first coupling portion and the second coupling portion has the at least one shaft member; the other one of the first coupling portion and the second coupling portion has at least one engaged portion which is a recess engageable with the at least one shaft member; characterized in that the at least one shaft member comprises: either a ball engageable with the at least one engaged portion or a piston provided with a pin engageable with the at least one engaged portion at one end of the piston; and at least one elastic body energizing the ball or the piston toward the at least one engaged portion in the direction of the bending axis.