PURPOSE: To eliminate an error by correction at each pitch for an efficient correcting operation, by positioning the extreme end of corrected positions corresponding to the predetermined pitch in the specified position in conjunction with the number of corrected positions depending upon a size of unbalance.

CONSTITUTION: In case when an amount of shift by a phase shifting circuit 7 is zero, a phase differences relative to the reference phase signals of square wave signals I, II become 0°, 90° respectively. A 2-element composite circuit 1 issues a signal A by DC signals (x), (y) and I, II. An amplitude of the signal A is proportional to a magnitude of unbalance of a specimen and further, a phase difference relative to the reference phase signal of the signal A has a definite relationship with an angular position in which an unblance of the specimem exists. A content of a memory circuit 4 storing a signal after rectification of the signal A turns out to be a detecting value of the magnitude of the unbalance of the specimen and further, by positioning the specimen in a position where the difference becomes 0 by comparison of output signals of phases of the signal A and a resolver (c), an unbalanced angular position of the specimen can be positioned in the definite position.