Abstract: A positioning device for positioning a mat in a car includes an elongated clamping base, at least one spring unit and a hook unit. The clamping base is formed with at least one lower clamping unit and at least one upper clamping unit having a rear edge hinged to a corresponding lower clamping unit. The spring unit is provided on the clamping base for biasing the upper clamping unit toward the corresponding lower clamping unit. The hook unit has a first end connected to the clamping base and a second end adapted to be hooked at a desired position in the car. The upper and lower clamping units are adapted to clamp an edge portion of the mat therebetween. The spring unit ensures tight engagement between the upper and lower clamping units and the edge portion of the mat.