A battery monitoring system includes a plurality of battery cells connected in series and including a first battery cell at a highest potential; a discharge circuit connected to a high potential side of the first battery cell through a first line; a circuit connected to the high potential side of the first battery cell through a second line; and a plurality of electro-static protection circuits each including one end portion connected to at least one of a high potential side and a low potential side of each of the battery cells, and another end portion connected to the first line.