PURPOSE: To compensate initial imbalance without changing the output display value to zero, by providing two adjustable transfer function circuits.

CONSTITUTION: Adjustable transfer function circuits 17, 18 of which transfer functions are A and K are provided between a first vibration detector 5 and an indicator 19, by way of pushbutton row 20. When pushbutton I is depressed, circuit I is made; when pushbutton II is depressed, circuit II, which is a compensation circuit, is made; when pushbutton III is depressed, circuit III, which is a calibration circuit, is made. Therefore, after performing compensation and calibration by depressing pushbuttons I, II, III, sucessively, when pushbutton I is depressed again, the output display value of the indicator 19 will indicate the imbalance vector of a rotating body 1 only. Thus, the initial imbalance may be compensated without resetting the output display value of the indicator 19 to zero.