An output unit, an input unit and an input-output system are provided to construct a safety control logic having a high degree of freedom in design and has scalability. The output unit includes an input signal receiving part, receiving an input signal from the input unit; and an output control part, performing an output based on the input signal. In each group set for the output unit, the output unit performs the output when receiving the input signals from all the input units set to the same group as the group set for the output unit.