Abstract: Displacement of a subject is measured easily and accurately from a distant point by attaching a displacement measuring target, where two or four light sources are fixed on a flat, substrate to a measured point of the subject, comprehending displacement correction coefficients (Kx, Ky) expressing a relation between intervals in X and Y directions on the subject and interval detecting voltages corresponding to the intervals on the basis of position detecting voltages corresponding to positions of the light sources obtained by projecting the light from the respective light sources onto a PSD light receiving surface of a PSD camera, detecting displacement of the light source caused by displacement of the subject by the light receiving surface to output the position detecting voltage, and computing a two-dimensional or three-dimensional displacement amount of the measured point on the basis of the position detecting voltages and the displacement correction coefficients (Kx, Ky).