A rotatable water treatment device including a hollow shaft and multiple filtering units is provided. The hollow shaft has an axis hole, an external wall and a plurality of through holes defined through the external wall and communicating with the axis hole. The multiple filtering units watertightly mounted on the external wall of the hollow shaft, and each of the filtering units includes a center hole, two clipping nets, a supporting net and two filtering membranes. The supporting net is mounted between the clipping nets and two filtering membranes sandwiches the clipping nets such that the filtering membranes can be prevented from sinking into the meshes of the supporting net with the pump effect to accelerate the conducting of the water-filtering.