The invention discloses a small multistage amplification laser device based on a cube-corner prism. The small multistage amplification laser device comprises the cube-corner prism, a pumping system, laser media, a Q switching module, a deflecting prism group, a rectangular prism and an output mirror, wherein the cube-corner prism, the laser media and the deflecting prism group are arranged according to specific positions, so that a light path can be subjected to spatial multipass folding so as to greatly reduce the volume of a traditional multistage amplification structure. Meanwhile, since the cube-corner prism is adopted, the anti-misalignment characteristics of the system are greatly improved, and the small multistage amplification laser device is an ideal device for obtaining miniaturization, high-reliability, high-power/large-energy and high-light-beam-quality laser output. The small multistage amplification laser device has the advantages of being simple in light path, compact in structure, easy in expansion and convenient in regulation, can be applied as an independent laser, also can be applied as a laser amplifier, and is especially suitable for engineering practical occasions which have requirements on laser performance, structural space and high reliability.