Disclosed is an ultra-short focus projecting optical system, which includes a display unit, a first lens group having a positive focus power, a second lens group having a positive focus power, a third lens group having a negative focus power, and an aspherical reflector arranged sequentially along a projection direction. The first lens group includes a first lens, a second lens and a diaphragm arranged sequentially along the projection direction. The first lens is a glass aspherical lens, the second lens is a glass spherical lens, and the first lens and the second lens are bent toward the diaphragm from their respective centers to their respective peripheries. The ultra-short focus projecting optical system and a projection device provided by this application can realize a large aperture and high resolution.