In operating the gear generating machine with a leading screw and a worm gear, which gives regular rolling motion to the gear blank, the minute errors of the leading screw and the worm in one revolution is called the cyclic error. To what degree the cyclic errors manifested on the profile of generated gear tooth was studied, and the following results were obtained. The effect of cyclic errors on the profile of the generated gear tooth can be divided into two cases ; (a) the irregular motion caused by the cyclic errors appears comparable to the same degree as the profile errors of the generated gear tooth, and (b) the effect appears in a greatly decreased degree on the tooth. The author calculated the degree of the diminutive of the cyclic errors, and obtained graphs of nondimensional equations for general use.