Abstract: A large-aperture laser amplifier side-pumped by a multi-dimensional laser diode stack, which comprises: multiple pumping light source assemblies; a laser medium, of which the shape is a prismoid, wherein both the upside surface and the underside surface of the prismoid are polygonal, and the number of the edges of the polygon is the same as the number of the pumping light source assemblies; and a cooling device. Each side of the laser medium is provided with a pumping light source assembly; the pumping light emitted from the semiconductor laser diode stack is shaped by the beam shaping element, coupled by the coupling duct, and then enters from the side of the laser medium for side-pumping, and thereby amplifying the laser beam incident from the upside surface of the prismoid of the laser medium.