An engineering tool includes a display area to display a ladder program, the display area being displayed on a display screen of a display device; and a cell, which is a temporal-operator imparted region. The cell, which is a temporal-operator imparted region, is a region that is displayed in the display area and in which a temporal operator is imparted to a program module of the ladder program. The engineering tool includes a control specification editing unit and a control-specification-descriptive-expression converting unit. The control specification editing unit creates the program module. The control-specification-descriptive-expression converting unit converts the program module into a mathematical expression that can be input to a model checking program.