PURPOSE: To provide a jib swing stop device which is constituted to raise a tower in a state to extend a jib to the front of a tower without being limited by the length of a jig to the length of a tower.

CONSTITUTION: A jib swing stop device for a tower crane comprises a stopper 5 attached to a lower jib; and a rotatable stopper support structure. The stopper support 6 consists of two side plate 6; and a support plate 6b to support the stopper 5. The ends on one side of the two side plates 6a are rotatably attached to a bracket 7, arranged on the upper surface of an upper tower 2a, by means of a pin 8. The end on the other side have support surfaces 6c making contact with the upper surface of the upper tower 2a during working of a tower crane. Further, a tension spring 9 through the force of which the stopper support 6 is held in a set position and a rope 10 to rotate it to a release position are provided.