A controller for machine tool 1 has a program analyzing section 12 for analyzing a machining program and extracting a fixed cycle command, a parameter setting section 15 for, on the basis of the extracted fixed command, determining an accuracy level being graded into a plurality of grades depending on how high machining accuracy is prioritized as compared with machining time in machining and setting parameters corresponding to the determined accuracy level and relating to control of the operation of a feed mechanism 30, and a drive control section 17 for controlling the feed mechanism 30 on the basis of the extracted fixed cycle command and the set parameters. The parameter setting section 15 calculates an arc-shaped movement trajectory of a tool moving around a virtual corner portion where two straight lines intersect with each other which corresponds to the parameters, and determines the accuracy level based thereon.