A reusing method of an end mill involves machining a base material of an end mill in advance so as to have coaxiality equal accuracy to coaxiality for a cutting part, and when the cutting part is worn out, cutting off of the cutting part and machining a new cutting part on a shank part while a part of outer peripheral surface of the shank part is left as margin without cutting. The new cutting part has accuracy of coaxiality and an outer diameter identical to those of the cutting part.

A workpiece processing method includes: a dresser preparing step of preparing a dresser of a predetermined thickness; a fixing step of fixing the workpiece and the dresser on a support member adjacently to each other in a first direction; a holding step of holding the support member by a holding table, after the fixing step is performed; and a cutting step of positioning a tool edge of the cutting blade at a predetermined height and cutting the workpiece and the dresser in the first direction by a cutting blade, after the holding step is performed.

A reusing method of an end mill 1, in which an end mill (1) has a margin which is a part of a circle having a diameter identical to a diameter of a shank part (3), the margin being provided on an outer edge of a cutting part (2), a base material of the end mill (1) is machined in advance so as to have coaxiality having equal accuracy to coaxiality for the cutting part (2), the shank part (3) is an unmachined part left without cutting the base material, the margin is a part of an outer peripheral surface of the base material left without cutting the base material when the outer edge is formed by cutting the base material, and when the cutting part (2) is worn out, the cutting part (2) is cut off and a new cutting part 2 is machined on the shank part (3) while a part of outer peripheral surface of the shank part is left as the margin without cutting, the new cutting part 2 having accuracy of coaxiality and an outer diameter identical to those of the cutting part (2).