Input/output module, standard input/output module unit and safety circuit unit

And power consumption and waste of parts are reduced. The input/output module (100) comprises a standard input/output module unit (4) and a safety circuit unit (5). The standard input/output module unit (4) includes: an external interface unit connected to a device to be controlled; a standard input/output module-side control unit that receives an input signal from the device to be controlled and transmits the input signal to the control module unit, or transmits a control signal received from the control module unit to the device to be controlled; and first connector parts (41, 81) having a plurality of connection points. The safety circuit unit (5) includes: a diagnosis unit that diagnoses the operating states of the device to be controlled and the standard input/output module unit; a second connector part (51, 91) having a plurality of connection points and capable of being freely inserted into and removed from the first connector part; and a safety circuit-side control unit that controls the operation of