A safety PLC includes an I/O module to which a safety device for detecting a predetermined condition at any time is connected, a CPU module that executes a safety program for managing the I/O module, and a communication unit that interconnects the I/O module and the CPU module with each other. The CPU module includes: a PIN code memory that stores a PIN code for authenticating that the safety program satisfies a predetermined standard; a PIN code input unit that allows a user to designate the PIN code; a program auto-creating unit that automatically creates the safety program; and a program authentication unit that puts the safety program into an executable condition when the PIN code designated by the user coincides with the PIN code stored in the PIN code memory.