The authors investigated the yarn irregularities caused by the different hardness of front top rollersi.e., 65$^{circ}$ 70$^{circ}$ 75$^{circ}$ 80$^{circ}$ 85$^{circ}$at the ring spinning frame and the results were as the followings; 1. The irregularity of the spun yarn (U%) was linearly increased with the hardness of front top roller and this tendency was significant statisticall. 2. Short-term additional irregularity caused by the front top roller largely affected to the amount of total yarn irregularity at the rate of 45%~80%. 3. IPI Values (thin place and thick place) of spun yarn was increased as the hardness of roller was increased and the increasing rate of IPI Value was large at the low count yarn in which the percentage of short fibre content was large.