One aspect of the present disclosure is a power-supply apparatus to supply an electric power to an electric working machine including a trigger switch, a motor, and a tool. The power-supply apparatus includes a connection detector, a trigger detector, and a signal outputter. In response to (i) the connection detector detecting connection of the electric working machine to the power-supply apparatus, and also to (ii) the trigger detector detecting an ON state of the trigger switch, the signal outputter outputs, to the electric working machine, a discharge prohibition signal prohibiting supply of the electric power to the motor, until an OFF state of the trigger switch is detected once by the trigger detector.