It is possible to easily and rapidly develop an inverter application while maintaining stable quality. Executable code modules which have been sufficiently tested are installed in an inverter. An application source code is created on a programming device by using function blocks corresponding to the executable code modules and connection lines for connecting the function blocks. The source code is complied to create a connection information table for selecting the executable code modules and specifying their execution order. The connection information table is downloaded to the inverter via communication to execute the application.