Abstract: A method for displaying a circular interpolation locus which is used in a numerical control apparatus. The method is constituted by the steps of detecting movements of axes controlled by the numerical control apparatus, synthesizing signals detected in the detected step, displaying a movement locus of two axes as a circular interpolation locus on a display. A numerical control apparatus which has a circular interpolation locus display function is also disclosed. The numerical control apparatus is constituted by first detecting unit for detecting a motion of a control object controlled by a first servo motor, second servo detecting unit for detecting a motion of the control object by a second servo motor, two axes synthesizing unit for synthesizing the output signals for the first detecting unit for displaying the two axes movement locus. The method and apparatus can be applicable both semi-closed loop and hybrid control.