A safety controller provides a safety output to a target controlled system such as a magnet contactor based on an input from an input device such as a safety door switch to thereby control operation of machine equipment. Safety output parts serve to transmit a solid-state output as the safety output and a connection output part transmits a connection output to another safety controller. A control part having two CPUs controls the safety output and the connection output according to a program based on the input from the input device. Two or more of such safety controllers are connected through their connecting output parts and the connecting input parts to together form a safety system.