A power-supply apparatus (1; 300), comprising: a connector (20; 331, 332, 333, 334, 335) configured to removably connect to an electric working machine (50; 500; 500A; 500B), the electric working machine including: a motor (60; 600) configured to generate a driving force by receiving an electric power; and a tool (65; 650) configured to be driven by the driving force generated by the motor; the power supply apparatus (1; 300) further comprising: a connection detector (12; 350) configured, in response to start of output of the electric power, to detect connection of the electric working machine to the power-supply apparatus; at least one battery (38; 380); a trigger detector (12; 350) configured to detect a state of a trigger switch (51; 510) of the electric working machine; and a signal outputter (12; 350) configured, 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, to output a discharge prohibition signal to the electric working machine until an OFF state of the trigger switch (51; 510) is detected once by the trigger detector, the discharge prohibition signal prohibiting supply of the electric power to the motor (60; 600). a connector (20; 331, 332, 333, 334, 335) configured to removably connect to an electric working machine (50; 500; 500A; 500B), the electric working machine including: a motor (60; 600) configured to generate a driving force by receiving an electric power; and a tool (65; 650) configured to be driven by the driving force generated by the motor; a motor (60; 600) configured to generate a driving force by receiving an electric power; and a tool (65; 650) configured to be driven by the driving force generated by the motor; the power supply apparatus (1; 300) further comprising: a connection detector (12; 350) configured, in response to start of output of the electric power, to detect connection of the electric working machine to the power-supply apparatus; at least one battery (38; 380); a trigger detector (12; 350) configured to detect a state of a trigger switch (51; 510) of the electric working machine; and a signal outputter (12; 350) configured, 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, to output a discharge prohibition signal to the electric working machine until an OFF state of the trigger switch (51; 510) is detected once by the trigger detector, the discharge prohibition signal prohibiting supply of the electric power to the motor (60; 600). a connection detector (12; 350) configured, in response to start of output of the electric power, to detect connection of the electric working machine to the power-supply apparatus; at least one battery (38; 380); a trigger detector (12; 350) configured to detect a state of a trigger switch (51; 510) of the electric working machine; and a signal outputter (12; 350) configured, 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, to output a discharge prohibition signal to the electric working machine until an OFF state of the trigger switch (51; 510) is detected once by the trigger detector, the discharge prohibition signal prohibiting supply of the electric power to the motor (60; 600).