Joining device for connecting two ends (12, 14) of at least one longitudinal conveyor belt, the joining device comprising at least: - a first joining plate and a second joining plate which are each configured to cover a different side of the ends of the conveyor belt such that said conveyor belt is interposed vertically between the two joining plates (18a, 18b), said joining plates (18a, 18b) forming a first pair of wings which is suitable for clamping a first end of the conveyor belt and a second pair of wings which is suitable for clamping a second end of the conveyor belt, the first pair of wings and the second pair of wings being arranged on either side of a joining plane, the joining plane extending transversely to the center of the assembly formed by the first joining plate and the second joining plate, - a device for securing said joining plates (18a, 18b) together, - a removable spacer which is configured to be interposed vertically between the first joining plate and the second joining plate in order to space said plates apart, and which defines a centering hole that is arranged such that a connecting element which secures the spacer to the joining plates (18a, 18b) can pass through said hole, characterized in that the spacer is suitable for being interposed between the wings of the first pair of wings such that the centering hole of the spacer is offset from the joining plane, in order to free the space defined between the second pair of wings, the spacer having an abutment face which is arranged so as to face the second pair of wings, and which extends at least in part along the joining plane, in order to form a stop for the conveyor belt along the joining plane when the spacer is in the assembled position. - a first joining plate and a second joining plate which are each configured to cover a different side of the ends of the conveyor belt such that said conveyor belt is interposed vertically between the two joining plates (18a, 18b), said joining plates (18a, 18b) forming a first pair of wings which is suitable for clamping a first end of the conveyor belt and a second pair of wings which is suitable for clamping a second end of the conveyor belt, the first pair of wings and the second pair of wings being arranged on either side of a joining plane, the joining plane extending transversely to the center of the assembly formed by the first joining plate and the second joining plate, - a device for securing said joining plates (18a, 18b) together, - a removable spacer which is configured to be interposed vertically between the first joining plate and the second joining plate in order to space said plates apart, and which defines a centering hole that is arranged such that a connecting element which secures the spacer to the joining plates (18a, 18b) can pass through said hole, characterized in that the spacer is suitable for being interposed between the wings of the first pair of wings such that the centering hole of the spacer is offset from the joining plane, in order to free the space defined between the second pair of wings, the spacer having an abutment face which is arranged so as to face the second pair of wings, and which extends at least in part along the joining plane, in order to form a stop for the conveyor belt along the joining plane when the spacer is in the assembled position.