A power supply apparatus includes an assembled battery including a plurality of cells, a plurality of temperature sensors sensing temperatures of the plurality of cells, respectively, a current sensor sensing a current flowing through the assembled battery, and a state monitoring unit and an abnormality detecting apparatus that are a detecting unit of detecting an abnormality of the plurality of temperature sensors. The detecting unit makes a notification of an abnormality, when charging or discharging of the assembled battery is performed and on a basis of a plurality of detections of the deviation being greater than a first prescribed value and the output fluctuation range being smaller than a second prescribed value.