A computing method for a simulation in which an article, a conveyor, and a table are plotted in a three dimensional simulated space, and in which the conveyor conveys the article includes setting a priority representing a degree at which the lifter is handled as a single unit as the article higher than another priority representing a degree at which the table is handled as a single unit as the article when the lifter moves the article placed on the table upwardly, and setting the priority representing a degree at which the lifter is handled as a single unit as the article lower than the priority representing a degree at which the table is handled as a single unit as the article when the lifter conveying the article moves downwardly below the table.