The present invention provides a battery carrier sliding device for the electric wheelchair, wherein a battery box for the electric wheelchair can be disconnected or reconnected through a manual lockable unit. The present invention provides an improved design for a battery carrier sliding device for the electric wheelchair that utilizes lockable units to manually detach or reattach the battery box by pulling or triggering the lockable unit. The lockable unit is comprised of a connecting belt and two flexible inserting units, wherein holes are formed on the supporting units respectively to correspond the flexible inserting units so that the battery box can be located securely onto the electric wheelchair. The battery box is comprised of a carrying function in such that the structures or the types of batteries do not need to be altered. Various types of batteries can be utilized with the present invention. The present invention provides an improved battery box that can fulfill the needs of the market.