A voltage detecting apparatus includes: an assembled battery made of plural cells, a self-diagnostic circuit, and a measuring part for measuring the plural cells or measuring a diagnostic voltage generated by the self-diagnostic circuit. Electric power is supplied to the self-diagnostic circuit by a charge pump circuit. The self-diagnostic circuit includes plural circuit elements connected in series, and a current path connected to the measuring part and formed in correspondence with each of the plural circuit elements, and the measuring part includes a multiplexer for switching a state of connection between each of the current paths and the circuit network. The measuring part determines whether or not the circuit network is normal based on a voltage dividing ratio by the circuit element corresponding to the current path switched by the multiplexer.