PURPOSE: To make the correction automatic thereby to accomplish the same easily in high accuracy by controlling the injection mechanism of a thermoplastic resin or a thermoset composite such that it can accomplish the injection in a quantity corresponding to the unbalance.

CONSTITUTION: The output signals of a switch circuit 12, which is turned on when a rotating body such as a motor rotor 1 comes to an unbalance position, is generated as operating signals b through a delay circuit 13, and at the same time the output corresponding to the unbalance is generated as signals a through a correction control circuit 9 from an unbalance measuring circuit 8. Both of the signals a and b are fed to the gate circuit 21 of an injector 16 to operate a solenoid valve 20 for a preset period so that a desired quantity of adhesive is injected from a nozzle 18 into the coil portion of the rotor 1 thereby to effect the correction of the unbalance. Thus, the correction is made automatic so that it can be accomplished easily in high accuracy.