According to one embodiment, a concentrator, which has a first surface on which a measuring device, which measures an amount of electric power consumption, is arranged includes a housing, a communication module, a wireless communication module, a control module, a first antenna, and a second antenna. The housing includes a first sidewall and a second sidewall which are opposed in a first direction orthogonal to a direction of arrangement of the measuring device and the concentrator. The control module notifies a server of amounts of electric power consumption by using the wireless communication module. The first antenna is provided in proximity to the first sidewall. The second antenna is provided in proximity to the second sidewall.