A positioning device includes a base, a press board, an antislip piece, and a positioning unit. The base includes an opening, and a mounting space. The mounting space is mounted on a rod. The press board is slidably mounted in the opening. The antislip piece is mounted on the press board and is close to the mounting space. The antislip piece is made of elastic material and is softer than the press board. The positioning unit includes a shaft mounted on the base and a driving member rotatably and eccentrically connected with the shaft. The driving member is driven between a pressing position for locking the rod and a releasing position for unlocking the rod. Thus, the user only needs to drive the driving member to lock or unlock the rod so that the rod is locked or unlocked easily and quickly.
