Workpiece machining method and workpiece machining device

A machining device for machining a workpiece into a desired shape, comprising:

• an end mill having a hemispherical lower end and rotating about a rotation axis to perform machining of the workpiece;
• a tool holding unit configured to hold the end mill;
• a positional deviation detection unit configured to detect a positional deviation between an actual contour line and an ideal contour line when the end mill is held by the tool holding unit, the actual contour line being a contour line of the end mill, and the ideal contour line being a contour line of the end mill having an ideal shape;
• a positional deviation correction unit configured to calculate a correction value for correcting the positional deviation between the ideal contour line and the actual contour line in each of a plurality of angular directions based on a center of the hemispherical shape, and correct the positional deviation of the end mill based on the calculated correction value;
• and
• a distance effect coefficient calculation unit configured to calculate a first distance effect coefficient indicating a degree of influence of the positional deviation when machining a second machining point, according to a distance between the end mill and the second machining point in a case where a machining point machined by the end mill transitions from one-point machining including a first machining point on a first machining surface in the workpiece to two-point machining including the first machining point and the second machining point on a second machining surface different from the first machining surface;
• wherein
• the positional deviation correction unit corrects a positional deviation of the first machining point based on the correction value when performing one-point machining using the end mill, and corrects the positional deviation based on the correction value at the first machining point and the first distance effect coefficient when a distance between the end mill and the second machining point approaches within a predetermined distance in a case where a machining point machined by the end mill transitions from the one-point machining to the two-point machining.