A battery module includes a plurality of battery cells, a plurality of holders, and a thermistor. Each of at least one of holders includes a thermistor holder. The thermistor supporter includes a pair of thermistor receiving segments, a pair of thermistor engagement segments, and a thermistor cover portion. The sensor casing includes a bias portion and an elastic claw portion. The bias portion is provided to press the sensor against one of the top surface and the bottom surface provided in the at least one of the battery cells by utilizing a reaction force generated by pressing the thermistor cover portion. The elastic claw portion has a width larger than the distance between the pair of thermistor receiving segments when the elastic claw portion is in a free state.