Packaging box with carton volume convenient to adjust

The packaging box comprises a packaging box body, two sets of cover plates are arranged at the upper end of the packaging box body, an adjusting plate is arranged at the bottom of the inner side of the packaging box body, and a lifting device is arranged at the lower end of the adjusting plate and located at the bottom end of the interior of the packaging box body. The lifting device comprises twosets of first movable rods and two sets of second movable rods, the upper ends of the two sets of first movable rods and the two sets of second movable rods are connected with the two sides of the lower end of the adjusting plate through connecting blocks, the two sets of first movable rods and the two sets of second movable rods are connected with the bottom of the packaging box body through a fixing plate, and a limiting groove is formed in one side of the fixing plate; limiting columns matched with the limiting grooves are arranged in the limiting grooves, movable blocks are arranged at the ends, away from the lim