Abstract: A method of and apparatus for searching for a fiducial point of machining in relation to the C-axis in a lathe capable of carrying out machining by C-axis control based on the C-axis origin. In a machining work applied to a workpiece having a C-axis-value-prescribed configuration whose C-axis value in relation to the fiducial point of machining is prescribed by a first angle, and second and third angles between the C-axis origin and each point of measurement located on the opposite sides of the C-axis-value-prescribed configuration facing the C-axis are measured, the angle between the fiducial point of machining and the C-axis origin is obtained on the basis of the second and third angles measured and the first angle prescribed between the C-axis-value-prescribed configuration and the fiducial point of machining, thus detecting the fiducial point of machining with respect to the workpiece having the C-axis-value-prescribed configuration.