suitable welding robot of fig3 exemplary fig1 is a configuration diagram showing a welding section of fig3 exemplary fig1 is a diagram showing an unloading section and a carrier changing robot and exemplary fig1 is a perspective view showing a carrier loading stand a front floor production system in accordance with a preferred embodiment of the present invention suitably comprises a drop lifter 10 carrier drop means a horizontal movement driving means 11 a carrier 12 a carrier loading stand 13 an unloading robot 14 a carrier changing robot 15 and a welding robot 16 in certain embodiments according to the present invention a welding line 17 and a return line 18 are suitably independently provided in consideration of production and working stability preferably the welding line 17 is suitably provided at the bottom of the system and the return line 18 is suitably provided at the top such that the carrier 12 is circulated through the welding line 17 and the return line 18 for the front floor production preferably the drop lifter 10 is an up and down movement means for dropping the carrier 12 accordingly the drop lifter 10 receiving the carrier 12 returned to the return line 18 preferably moves down to transfer the carrier 12 to the welding line 17 and then is suitably returned to the original.