The utility model discloses an unlocking device for a battery box. The unlocking device comprises a support, and a lead screw spirally assembled on the support; a handle is arranged at one end of the lead screw; and a push-pull disc is fixed to the other end of the lead screw, and is used for being extended into an internal hole of a locking head to be matched with a plug inside in a blocking way. When in use, the lead screw is rotated to drive the push-pull disc to extend into the internal hole of the locking head; when the push-pull disc completely passes through the plug, the support is moved to drive the push-pull disc to block the plug, and the support is propped and pressed on the battery box, the lead screw is rotated in an opposite direction, the locking head is driven to move by the push-pull disc, and as a result, the battery box can be unlocked. The unlocking device for the battery box is convenient and fast to operate and simple in structure.