To make detectable a small vibration while enlarging it mechanically.

One end of a plate 2 is fixed to a part 1 to be measured for detecting vibration, and a converter 3 using a piezoelectric element or the like is mounted to one portion of the plate 2. When the plate 2 is fixed to the part 1 to be measured with vibration. to be measured in this manner, a standing wave due to vibration is transferred from the part 1 to be measured to the plate 2. In the plate 2, the vibration causes the collision of molecules and is enlarged to some extent, and energy leaks onto a surface from the plate 2. The vibration that is enlarged by the plate 2 is taken out as an electrical signal by the converter 3, and the level and frequency of the vibration are measured at the part 1 to be measured using an oscilloscope or a spectrum analyzer.