The utility model discloses a dual purpose machine for a loading and unloading ship. Hinged supporting seats of a front door frame and a rear door frame of a ship loading machine are connected with hinged supporting seats of a front door shelf and a rear door shelf of a ship unloading machine through pin shafts. The hinged supporting seats of the front door frame and the rear door frame of the ship loading machine and the ship loading machine use two door legs. The other two door legs of the ship loading machine are arranged on supporting seat which are provided with travelling wheel vehicles. A tower cap of the ship loading machine are concentric with a rotary bearing of a tooth ring up and down, which can lead a rotary part of the ship loading machine to rotate according to an upper rotary center and a lower rotary center. A center adjusting roller bearing and a thrust center adjusting roller bearing are arranged in the tower cap, and a rear pull rod is connected with a hinged supporting seat which is arranged on a cross beam which is arranged above the rear door frame of the ship loading machine and the tower cap of the ship loading machine through two connection points. A horizontal pull rod is connected with a hinged supporting seat which is arranged on the top of the rear door shelf of the ship unloading machine and the tower cap of the ship loading machine through the two connection points. A tail vehicle is rigidly connected with a lateral truss which is arranged in the ship unloading machine, and a leather belt of the tail vehicle and a leather belt of the ground surface are shared. The utility model has wide use prospect to transshipment docks.