To adjust the lift of a flying object flying at speeds from transonic to hyposonic according to its flying speed.

This lift adjusting device situated at the lower part of a flying object 1 is operated to adjust the lift of the lifting object 1. This device comprises a wave rider 2, formed so that a pair of fins 6 are situated on both sides of a wedge type wedge body 5, and an adjustment system 3 to adjust a protrusion amount of the wave rider 2 from the under surface 1a of the flying object 1. By regulating a protrusion amount of the wave rider 2 according to the flying speed of the flying object 1, the lift of the flying object 1 is regulated. The lift adjusting device regulates a protrusion amount of the wave rider 2 according to each flying speed of the flying object 1 and effectively improves a lift.