a thermal displacement correction method is provided , including the steps of presetting coordinate data for a fixed position of a workpiece on a table , finding an amount of displacement of the fixed position of the workpiece at a current cutting edge position based on the detected temperature , the coordinate data of the cutting edge position , and the coordinate data of the fixed position , and computing a difference in the coordinate data between the fixed position of the workpiece and the cutting edge position , finding an amount of displacement of the workpiece between its fixed position and the cutting edge position based on the detected temperature and the difference in the coordinate data between the fixed position and the cutting edge position , and computing a sum of each amount of displacement to define an estimated value and correcting thermal displacement using an nc unit based on the estimated value .