Abstract: A hinge structure includes a pivot shaft, a bracket, a fastening member, and at least one external tooth washer located between the bracket and the fastening member. The bracket and the external tooth washer are sequentially mounted on the pivot shaft and the fastening member is screwed to a tightening section at an end of the pivot shaft. The pivot shaft and a mounting arm of the bracket are respectively connected to a mainframe and a screen of a clam-type electronic apparatus, such as a notebook computer. The external teeth of the external tooth washer are firmly and elastically compressed between the bracket and the fastening member, preventing the fastening member from turning along with the screen when the latter is pivotally turned relative to the mainframe, or separating from the pivot shaft after the screen has been pivotally turned many times.