To provide a vibration detecting device capable of accurately grasping a chattering frequency and further accurately calculating a stable rotational speed.

A vibration detecting device comprises a sounding device 8 capable of outputting sounds of various frequencies, and the sounding device 8 outputs a sound of a frequency corresponding to a signal component with a maximum sound pressure in a detection range precedently set, so that an operator may compare a vibration sound with the output sound. Therefore, although a microphone 2 unavoidably detects sound pressures of sounds generated around a rotation shaft housing 1 including a vibration sound generated from a rotation shaft 3 under rotation, the operator may remove various noise from the detected sounds so as to accurately grasp a chattering frequency of the vibration sound derived from chattering vibration. A stable rotational speed at which a higher effect to suppress the chattering vibration may be exhibited than by a conventional technique may be obtained by calculating a stable rotational speed on the basis of the chattering frequency.