Battery box for railway vehicle

A receiving connector 6A and upper and lower guide sockets 7 are mounted on an attachment 9, and the attachment 9 is mounted on a casing 3A by means of a bolt member 16 so that positioning of the attachment 9 is adjustable. Guide rails 5A guide wheels 4 of the movable tray 1 having a connector 6B. Upper and lower guide pins 8 are respectively inserted into the upper and lower guide sockets 7 to be guided. Thereby, the attachment 9 is moved and connectors 6A and 6B are smoothly connected to each other while being aligned.