A battery pack includes a plurality of bare cells electrically connected in series or parallel to one another, and a protection circuit module provided with a thermistor. In the battery pack, the protection circuit module is electrically connected to the bare cells, and the thermistor is provided to be parallel in the length direction of the protection circuit module between the bare cells and the protection circuit module so as to measure a variable resistance by sensing a temperature of the bare cells and to transfer the measured resistance as an electrical signal to the protection circuit module.