This screen creation device for assisting in creation of a user interface screen of a numerical value control device stores components that are arranged on the user interface screen and composite components obtained by combining components, acquires mechanical information about a machine tool to be controlled by the numerical value control device, stores the mechanical information, the composite components, and creation rules for the user interface screen in association with one another, determines whether the user interface screen being created complies with the creation rules associated with the mechanical information about the machine tool to be controlled, and notifies the user of the user interface screen not complying with the creation rules.