A positioning device includes a battery box having a first connection base and a second connection base on two ends thereof. The first connection base has two first positioning members on two sides thereof. A first fixing base includes a first reception space for receiving the first connection base and the first fixing base is pivotable relative to the first fixing base. A second fixing base is connected to the second positioning portion. The positioning recess guides the positioning members on the first connection base to slide and pivot. The second connection base is connected to the second fixing base. The battery box is easily taken out and installed.