The utility model discloses a balanced single-nose bridge girder erection machine, which comprises a girder, a rear supporting leg, a front supporting leg, an intermediate supporting leg, a crane trolley and a carrier, wherein the rear supporting leg, the front supporting leg and the intermediate supporting leg are mounted on the girder, the crane trolley is arranged on the girder, and the carrier is arranged independently. Besides, the girder is a dual-straddle type girder, a horizontal and vertical walking mechanism is arranged on a lower crossbeam of the intermediate supporting leg, and the girder is provided with a lifting mechanism used for controlling and lifting displacement of a crossbeam of the rear supporting leg. Each supporting leg has a function of extension and can realize longitudinal slope regulation, the front supporting leg is provided with a swaying function and can get a bridge abutment in an extension form, thereby bringing convenience for erecting head and tail bridges and realizing longitudinal moving and span changing along the girder. The intermediate supporting leg can move transversely and longitudinally, and a hanging beam trolley with swaying functions can sway side beam in place at one step via eccentrically hanging. The balanced single-nose bridge girder erection machine is compact in structure, light in weight, convenient in transport and assembly, high in automation degree and working efficiency and the like.