A power supply adapter according to one aspect of the present disclosure includes a power cord, a power-source attachment portion, a working-machine attachment portion, a temperature detector, and an overheat determiner. The temperature detector is configured to detect temperature of the power cord and to output a detection signal indicating the temperature detected. The overheat determiner is configured to determine that the power cord is in an overheated state based on the detection signal from the temperature detector and to output an overheat determination result indicating that the power cord is in the overheated state.