To make a highly precise surface working executable without performing a trial working.

In this workpiece surface working method by numerical control, the surface Wa of a workpiece W is worked by moving the workpiece W or a tool T to an X axial direction and a Z axial direction by an X moving motor Mx which is controlled based on a numerical value for X axial direction control corresponding to the X axial direction target position of the workpiece W or the tool T and a Z moving motor Mz which is controlled based on a numerical value for Z axial direction control corresponding to the Z axial direction target position. In this case, the Z axial direction mounting amounts of the workpiece W or the tool T at the time of rotation-driving the X moving motor Mx and the Z moving motor Mz are detected, and the Z axial direction actual position being the actual Z axial direction present position of the workpiece W or the tool T is detected based on the Z axial direction moving amounts, and the workpiece surface Wa is worked by correcting the numerical value for Z axial direction control so that the Z axial direction actual position can be made coincident with the Z axis direction target position.