The invention discloses a displacement adjusting device which comprises a support, a guiding component, a micro-adjusting component, a micro-displacement meter and a driving component. Specifically, the guiding component is arranged on the support, the micro-adjusting component is arranged on the guiding component in a movable mode in a first straight line direction and a second straight line direction, the micro-displacement meter is movably arranged on the micro-adjusting component in a movable mode in a third straight line direction, wherein the first straight line direction, the second straight line direction and the third straight line direction are perpendicular to one another, the driving component is used for driving the micro-adjusting component to move, and the micro-adjusting component is respectively connected with the guiding component and the micro-adjusting component. The displacement adjusting device can be used for detecting the micro displacement of each actuating point of a deforming mirror quickly, efficiently and accurately, and accordingly high stress adjusting accuracy is achieved.