A connecting device of the invention is used to connect two members together. The connecting device is formed of a base flange, a support column extending downwardly from the base flange, and elastically deformable engaging members formed at both lateral sides of the support column and projecting from the base flange. The support column has first and second side edges, and the lateral sides extending between the first and second side edges. The distance between the first and second side edges is greater than that between the lateral sides. The first side edge is cut diagonally from a longitudinal middle portion of the support column to a lower end portion of the support column, and the second side edge is cut diagonally from near a top of the support column to the lower end portion. The engaging members have lower ends terminating at and joining with the lower end portion. Each engaging member has a circular arc shape in a lateral cross section and extends from near the first side edge to cover a middle of the width at one lateral side, and an enlarged portion extending laterally outwardly from the support column at the longitudinal middle portion of the support column. The connecting device can be used repeatedly for connecting the two members together.