In a battery pack having a housing, battery modules composed of a plurality of battery cells, acquisition units equipped with slave antennas, and a monitoring device equipped with a parent antenna, the monitoring device and the acquisition units perform wireless communication to obtain battery information such as a state of change of each battery cell. A radio wave absorption part is formed on at least one of surfaces of the housing and an inside part of the housing. The radio wave absorption part absorbs a part of radio waves emitted from the parent antenna and the slave antennas.