A battery case for a robot has a housing and an end cap. The housing defines a chamber for receiving a battery therein. The chamber has an open end. The end cap includes a cap that is used to cover the open end, a rotatable post rotatably passing through the cap and extending into the chamber, an elastic member arranged around the rotatable post and comprising an end abutting against the cap, and a locking member connected to the rotatable post and rotatable together with the rotatable post to a position where the locking member is engaged with the housing, thus locking the cap to the housing.