To provide a displacement detection apparatus capable of detecting a displacement in the height direction of a member to be measured, with a high precision, and also capable of performing a high-speed and stable measurement. A first light flux L1 serving as object light is caused to enter a member to be measured 5, and reflected light thereof is caused to enter again the member to be measured 5 after being diffracted by a first diffraction grating 7. Then, the second-time reflected light of the first light flux L1 by the member to be measured 5 is diffracted by a second diffraction grating 9. By diffracting the first light flux L1 by the second diffraction grating 9, a change of the optical path length caused by tilting of the member to be measured 5 is cancelled.