To provide a control method capable of making feeding accuracy in the Y axis direction highly accurate when moving a tool post in the direction of Y axis as a composite moving axis.

In a method for controlling a movement of the tool post in the Y axis direction of this NC lathe arranged so that the tool post moves in the Y axis direction of the direction orthogonal to the Z axis and the X axis by simultaneously moving the tool post in the respective directions of the X axis and the sub-moving axis for crossing at a prescribed angle with this X axis, a moving area in the X axis direction of a cross slide is divided into plural areas. An error quantity of an actual movement relative to a command value when moving the tool post in the Y axis direction is detected in the divided respective areas to calculate a distributed error quantity by distributing the detected error quantity to the respective X axis and sub-moving axis directions, and when moving the tool post in the Y axis direction in the respective areas, respective actual moving quantities in the X axis and the sub-moving axis are corrected according to the distributed error quantity in the area.