PURPOSE: To obtain the static unbalance quantity which is not influenced by the rotating face and has no turning displacement angle error, by linking mechanically the supporting material in the side, to which the displacement angle detecting means is linked, to the end part of the object to be measured.

CONSTITUTION: The displacement angle detecting means consisting of slit disc 25 and photosensor 28 and torque transfer plate 26 are fitted in the end part 41 side of supporting shaft 39. Permanent magnet 30 at the tip of driving shaft 29 is opposed to torque transfer plate 26 to constitute torque adding means 44. Recess 47 formed on rotation shaft 23A is fitted to pointed tip part 41 of supporting shaft 39, and pointed tip part 41 of supporting shaft 40 is fitted to recess 47 formed on rotation shaft 23B, thereby supporting rotating material 22 rotatably between supporting shafts 39 and 40 without shaking.