A voltage measuring apparatus is configured to measure voltage between a positive terminal and a negative terminal of a device, and the voltage measuring apparatus includes: a PTC thermistor that is connected to one of terminals of the device; and a measuring circuit that measures voltage of one of the terminals through the PTC thermistor with respect to a specified reference potential and voltage of the other of the terminals with respect to the reference potential. The voltage measuring apparatus detects temperature abnormality of the device or components associated with the device.