A method for post-curing a 3D printing output and a transparent orthodontic device manufactured by the method are described. The method for post-curing a 3D printing output removes residual resin from printouts manufactured through a 3D printer, shortens the curing time by improving the curing speed through a post-curing process, and can manufacture printouts with improved strength and increased transparency. The transparent orthodontic device removes resin of the surface through the post-curing process when manufacturing a transparent orthodontic device, improves strength, not only has excellent transparency, but also enables unreacted monomers to be removed, and can exhibit shape memory characteristics that restore its shape to the initially printed-out shape of the transparent orthodontic device by the provision of heat.