It is an object of this invention to provide an optical member that is able to cut ultraviolet rays without employing means such as addition of an ultraviolet absorber to the resin, using an ultraviolet cut filter or using ultraviolet absorption coating, as well as a thermoplastic resin to be used for the optical member. The thermoplastic resin of the invention comprises a spatial structural component unit, wherein the spatial structural component unit includes four or more aromatic groups selected from the group consisting of monocyclic aromatic groups and fused polycyclic aromatic groups, the spatial structural component unit has three or more monocyclic aromatic groups and/or heterocyclic aromatic groups in a conjugated structure, or one or more monocyclic aromatic groups and one or more fused polycyclic aromatic groups in a conjugated structure, or two or more fused polycyclic aromatic groups in a conjugated structure, and in a 0.1 mass % dichloromethane solution, the light transmittance at a wavelength of 355 nm is lower than 20% and the light transmittance at a wavelength of 500 nm is 90% or higher.