A programming assist device for a PLC program and a programming assist method for a PLC program capable of easily preparing separate executable files for causing redundant CPUs of a PLC to operate and reliably preventing an emergency stop of the PLC due to a failure in converter software are provided. First and second intermediate codes are generated from an original program. An inverse conversion program is generated from the first intermediate code. A reconverted first intermediate code and a reconverted second intermediate code are generated from the inverse conversion program. In the case where the intermediate codes and the reconverted intermediate codes match each other, a first executable file is generated from the reconverted first intermediate code, and a second executable file is generated from the reconverted second intermediate code. The executable files are transferred to the PLC.
