Abstract: The present invention relates to an apparatus for detecting and indicating the balance of a rotating body such as a grinding wheel, a spindle or the like in a machine tool such as a grinding machine. The apparatus comprises an original-point detecting means for detecting an original point on the rotating body, a vibration detecting means for detecting vibration caused by an unbalanced condition of the rotating body, an arithmetic means for computing, from the detected vibration, a deviation of said rotating body in each of a plurality of index positions on the rotating body which are angularly spaced from said original point as a reference, a deviation display means for displaying the maximum value of the deviations, and an unbalanced position indicating means for indicating one of the index positions based on the computed deviations.