To provide a mechanical detector and a detection device with little affection to a specimen by light irradiation, also with a high sensitivity.

The mechanical detector provided with a cantilever 21 of a semiconductor material, detects highly sensitively a minute force mechanically impressed on the cantilever 21 by detecting the elastic deformation of the cantilever 21. The mechanical detector comprises the detection means (wave length variable laser light source 22, optical detector 23) for detecting the elastic deformation of the cantilever 21 from the variation of the transmitted spectrum from a semiconductor material 21A of the cantilever 21.