To provide a method for setting positioning accuracy and a positioning accuracy setting device, capable of satisfactorily maintaining positioning accuracy of a feeding mechanism at a degree equal to or less than a desired positioning accuracy, regardless of expansion/contraction of the feeding mechanism.

An operator measures positioning errors a plurality of times at five positions in a movable range of a table 201 displaced by a feeding mechanism 204 by using a machine tool 200 and an external computer device 300. The operator sets a standard deviation of the measured positioning errors as an error value by using the external computer device 300, and then sets a difference between the range of the error value and a desired error value as a correction value of an inside measuring position at the respective measuring positions, and generates correction value setting information by setting a correction value smaller than the correction value of the inside measuring position as the correction value for other four measuring positions. The operator generates a correction value table that sets the correction value on the basis of correction value setting information in a plurality of correction sections set in the movable range of the table 201, by using the machine tool 200.