To provide a moving amount detecting device wherein the moving amount of a moving object to-be-measured is detected in real time with high precision.

A measurement device 3 is so allocated as to collimate a center-axis center part of a cylindrical reflection target 2, while a CCD camera 4 is so allocated that the optical axis of the CCD camera 4 agrees with a collimation axis of the measurement device 3. With the direction of horizontal component of measurement device 3's collimation axis as a Y axis, while such horizontal direction orthogonal to the Y axis as an X axis and vertical direction as Z axis, the moving amount in the X axis and the Z axis of the reflection target 2 is obtained by converting the moving amount of the gravity center of reflection target 2's orthogonal projection in the imaged screen of the CCD camera 4 into an actual moving amount, while the moving amount in the Y axis direction is detected based on a distance-difference between a corrected distance which is obtained by correcting a found distance by the measurement device 3 with the moving amount in X axis direction and a measured value in initial state. Then, based on these moving amounts together with a position coordinate of the reflection target 2 in initial state, a current position coordinate of the reflection target 2, or a target object 1, is detected.