This study is to determine the exact position of tipping rotation center of root. The method of measurement is to record by means of dial gauge. The different shapes of root of lower second premolar are named as smooth type, tapered type, and curved type. The followings are the result ; 1. The tipping rotation center of the teeth varies with he shape of roots. 2. The rotation center of the root is placed apical one third portion upon roots in the smooth shape of roots, one half portion of roots in the taper shape of roots and below the apical one-third of root in curve shape.