1. A common parameter interface generation program that generates a common parameter interface in a line design tool which generates line design information of a control system having models of control devices arranged therein, a mechanical design tool which selects a control device on the basis of the line design information and generates mechanical design information, and a control design tool which generates control design information of a mechanical operation on the basis of the mechanical design information, the common parameter interface generation program being configured to cause a computer to perform: an identification information assigning step of assigning identification information for identifying the control device in the acquired line design information; a parameter acquisition step of acquiring a list of parameters of the selected control device, which are used in the mechanical design information and the control design information, from a design information storage unit; a common parameter generation step of associating the acquired list of the parameters with the identification information and the names of the selected control device in each of the design information to generate a common parameter and of registering the common parameter in a common parameter storage unit that stores a parameter used in common by the line design tool, the mechanical design tool and the control design tool; and a common parameter interface generation step of generating, in each of the design tools, a common parameter interface that acquires the value of the parameter of the control device from the common parameter storage unit when the design information is read and reads out the value of the parameter to the design information in a data format in data format definition information which defines the data format required when the parameter is treated in the line design tool, the mechanical design tool, and the control design tool.