A circuit for detecting battery cell abnormalities in a multi-cell series battery for effectively and quickly detecting abnormalities with a simple, small circuit that provides improved reliability, safety and service life of the multi-cell series battery. In the voltage monitoring device 12, immediately after the start of the monitoring cycle of any battery cell BTi, cell voltage abnormality detector 14 checks whether cell voltage Vi is outside of the normal operating range. The cell voltage abnormality detector 14 has: a group of selection switches 18 for selecting any battery cell BT of multi-cell series battery 10 and retrieving its voltage to first and second monitoring terminals A, B; cell voltage/monitoring current converter 20; monitoring current/monitoring voltage converter 22; comparison/evaluation circuit 24; evaluation signal output circuit 26 and abnormality detection controller 28.