The invention relates to a device for manufacturing a period-variable photonic crystal on the basis of multiple beam interferometry, and relates to photonic crystals. A laser device, a spatial filter, a diaphragm, a convex lens, a multi-beam generation component and a photoresist plate are arranged successively; a light outlet of the spatial filter is arranged in a focus of the convex lens; after the spatial filter carries out beam expanding on laser emitted by the laser device, the laser is changed into a beam of diverging light, the diverging light is changed into a beam of parallel light when passing the convex lens, the beam of parallel light irradiates on the multi-beam generation component along the normal direction, the multi-beam generation component adjusts an optical path of the beam of parallel light to generate multiple coherent light beams, the multiple coherent light beams are overlapped on the photoresist plate, single exposure is carried out on an overlapped interference area of the multiple beams on the photoresist plate, and the period-variable photonic crystal is obtained via development.