A spot welding quality check system, which can be easily used and can be adapted to various situations. The check system has: a pair of electrodes configured to move toward or away from each other and apply current to a workpiece while pressurizing the workpiece; a displacement detecting part which detects an amount of displacement between the electrodes during spot welding; a checking part which estimates as to whether welding quality is good or poor by using an inner function, based on the detected amount of displacement; a correction receiving part which receives a correction by an operator regarding the estimated welding quality; and a learning part which updates the inner function based on an estimation result when the correction receiving part does not receive the correction, and updates the inner function based on a content of the correction when the correction receiving part receives the correction.