The laser amplification apparatus is provided with a plurality of plate-shaped laser medium components (M1 to M4) which are disposed to be aligned along a thickness direction, and prisms (P1 to P3) which optically couples the laser medium components. Each of the laser medium components is provided with a main surface to which a seed light is incident, and a side surface which surrounds the main surface. An excitation light is incident from at least one side surface of a specific laser medium component among the plurality of laser medium components. The excitation light is incident through the prism to a side surface of the laser medium component adjacent to the prism.