The invention relates to a multifunctional screw locking device for an automobile seat, and belongs to the technical field of automobile assembly tools. The multifunctional screw locking device comprises a screw gun body, an end cover, a gun handle, a connection barrel, a connection ring, a bearing sleeve, an end sleeve, a rotating shaft, a motor, a speed reducer, a switch, a multifunctional gun head, a connecting piece, a carbon arm and a spherical universal joint. Two types of gun heads are integrated together, the automobile type is manually recognized, switching between a hexagonal screw sleeve head and a wedge rod can be achieved through the effect of a spring, and tightening of different screws is achieved. Tightening of different screws can be achieved only by arranging one gun for each station, the cost is saved, and the problem that operators replace screw guns without stop is avoided. Meanwhile, the lower end of the carbon arm is rotationally connected with the connecting piece through a pin shaft, the screw locking device can only move in the up-down direction rather than swinging in the left-right direction when tightening the screws, and the gun body is prevented from hitting the wrist. The multifunctional screw locking device is high in practicability, wide in application range and high in safety.