PURPOSE: To execute a rational balancing work in a short time, by supporting a rotating body having plural inherent frequencies by a nonlinear supporting mechanism, collecting vibration data in each revolving speed in case when the rotating body reaches an allowable amplitude, calculating a correcting face and a correcting quantity, and irradiating laser light to the rotating body.

CONSTITUTION: A rotating body 1 reaching a revolving speed f1 is supported by a forcedly supporting body such as a guide roll, etc. and the rotating body is further accelerated. As a result, a supporting mechanism 10 is protected by the forcedly supporting body 11, also the amplitude of the rotating body 1 increases and a stable rotation is slightly lost, but the rotating body passes through a dangerous speed without contacting a static body. When the rotating body 1 passes through the first dangerous speed, it executes a stable rotation for a while. Subsequently, when it reaches a revolving speed f2, it approaches the second dangerous speed, therefore, the amplitude increases and becomes an allowable amplitude aB again. In this state, the vibration data at this time point is collected by a vibration meter 4, and this data is inputted to an arithmeticdevice. The arithmetic device calculates a correcting face and a correcting quantity by use of the vibration data by the stored revolving speed f1 and the vibration data by the revolving speed f2.