The microobjective optical system and the optical device provided in the present disclosure use a catadioptric structure. Specifically, a catadioptric relay lens group and a complex transmissive collimating lens group are combined to effectively correct a higher-order spherical aberration, and control astigmatism, field curvature, and primary and higher-order coma related to a field of view. In a spectrum band ranging from 320 nm to 800 nm, the field of view is larger than 2 mm, a numerical aperture is 1.0, and imaging quality reaches a diffraction limit.