To provide a polarity free battery box in which any one can set a battery easily without being aware of the polarity thereof.

A bridge diode 24 having an AC input terminal 26 and a DC output terminal 38 is fixed to a part of a case 18 for housing a battery 12. One of a pair of the AC input terminals 26 of the bridge diode 24 is connected with a contact 20 which is in contact with a positive electrode 14 of the battery 12, and the other of the AC input terminal 26 is connected with a contact 20 which is in contact with a negative electrode 16 of the battery 12. A lead wire for connection with the terminal of appropriate polarity of a circuit being driven by the battery 12 is then connected with the DC output terminal 38. The battery box may be used both in parallel connection and series connection.