A spatter production information storage unit stores spots where spatter has been produced. For the spots where spatter has been produced, a comparison information generation unit acquires weld design information stored in a design information storage unit and weld instruction information stored in an instruction information storage unit, compares both pieces of information, and generates comparison information. An image information output unit outputs the generated comparison information to a display device. The display device displays the comparison information on a screen so as to allow checking by an operator. Hence, it is possible to check, on the screen, comparison information for weld instruction information and weld design information highly likely as a cause for spatter being produced, and to efficiently perform the task of analyzing the causes for spatter being produced.
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