WELDING ROBOT SYSTEM

PROBLEM TO BE SOLVED: To provide a welding robot system capable of calculating a gap length without using any welding part detector of a non-contact type sensor.SOLUTION: In the welding robot system, the upper electrode reference position-calculating circuit 4 of a spot welding robot SR calculates an upper electrode reference position when an upper electrode 1a is brought into contact with a lower electrode 1b before performing the spot welding, a gap length detection time upper electrode position-calculating circuit 5 calculates the gap length detection time upper electrode position when the upper electrode 1a is brought into contact with a base material W when performing the spot welding while placing the base material W on the lower electrode 1b, and a gap length calculating circuit 10 calculates the gap length GL from a sheet thickness, the upper electrode reference position and the gap length detection time upper electrode position, and the spot welding is performed. An arc welding robot AR changes the welding conditions according to the gap length GL, and performs the arc welding. The gap length GL can be calculated simultaneously with tack welding.