To provide a control device capable of controlling the variability of the dimension of a cut width while retaining the precise uniformity of a pitch between two continuous knives of a knife shaft.

This electric machine control device 5 which enables the measurement of a difference of an actual position to a theoretical position of the knives 30 installed around the circumference of the knife shaft 1 is provided with a main support part 26 fixed to a reciprocating base 6 for a grinding device, an arm 27 fixed to the main support part, and a measurement assembly 60 fixed to the arm. The measurement assembly is provided with a first reciprocating base 41 substantially moving parallel to the axis of the knife shaft, a second reciprocating base 28 substantially orthogonally to the first reciprocating base, a first sensor 43 fixed to the second reciprocating base, a fixed support part 70 of a first diamond point 8 fixed to the first reciprocating base and moving with the first reciprocating base, a measurement assembly fixed to the fixed support part and provided with a movable support part 45 of a second diamond point 16, and a second sensor 47 fixed to the fixed support part.