Disclosed is a voltage monitoring apparatus wherein a first monitoring circuit (50) and a second monitoring circuit (60) having exactly the same configurations, respectively, are provided, and the threshold values of switching sections (51, 61) respectively provided in the monitoring circuits (50, 60) are switched to same values by means of a threshold value switching section (41). Then, a reference voltage and the threshold values are compared with each other by means of respective comparators (53, 63), the comparison results are outputted from respective comparators, and the outputs from respective comparators (53, 63) are compared with each other by means of an abnormality detecting section (42), thereby detecting a characteristic shift of the threshold values of the monitoring circuits (50, 60).