The invention discloses a soil improvement machine and a soil improvement method. The soil improvement machine comprises a rack, a surface soil processing assembly, a deep soil processing assembly, a deep soil paving plate and a surface soil paving plate, wherein the surface soil processing assembly and the deep soil processing assembly are arranged on the rack; the surface soil processing assembly comprises a surface soil cutting assembly, a surface soil elevator and a surface soil conveyor, and the surface soil conveyor is used for conveying soil backwards; the deep soil processing assembly comprises a deep soil cutting assembly, a deep soil elevator and a deep soil conveyor, and the deep soil conveyor is used for conveying the soil backwards; the deep soil paving plate is arranged on the rack and is positioned behind the deep soil cutting assembly; the surface soil paving plate is arranged on the rack and is positioned behind the deep soil paving plate; the distance between the bottom part of the deep soil cutting assembly and the earth surface is greater than the distance between the bottom part of the surface soil cutting assembly and the earth surface, and the distance between the bottom part of the surface soil paving plate and the earth bottom is greater than the distance between the deep soil paving plate and the earth bottom. According to the soil improvement machine and method disclosed by the invention, surface soil and deep soil are sequentially excavated, the surface soil is deeply buried, the deep soil is buried above the surface soil, and the purpose of exchanging soil layers can be achieved.