There is provided an optical displacement detection mechanism in which, even if a measurement object changes, a detection sensitivity and a ratio of a noise are adjustable without depending on optical characteristics such as reflectivity, or a shape and mechanical characteristics of a measurement object, an influence of a thermal deformation of the measurement object by an irradiated light to the measurement object can be made small, and a measurement accuracy can be ensured under optimum conditions. In an optical displacement detection mechanism comprising a light source irradiating a light to a cantilever becoming the measurement object, a light source drive circuit driving the light source, a photodetector receiving the light after irradiated to the cantilever from the light source to thereby detect an intensity of the light, and an amplifier amplifying a detection signal of the photodetector at a predetermined amplification rate, there is made such that, by providing a light intensity regulator and an amplification rate regulator, an irradiated light intensity to the cantilever and an amplification rate of the photodetector can be made variable.