A movement assisting tool (23) includes an attachment portion (24) that can be attached to and removed from a main body portion (11) of a battery unit (4), leg portions (25) that are coupled to the attachment portion (24) and extend from the attachment portion (24), and moving wheels (26) that are supported by extension portions of the leg portions (25). In a state where the attachment portion (24) has been attached to the main body portion (11) of the battery unit (4) and the moving wheels (26) are touching the ground, the battery unit (4) can be kept in an inclined orientation in which the wheels (13) are touching the ground and ground contact portions (14) are raised above the ground.