A method for 3D preprocessing for ray tracing includes: selecting and storing visible surfaces by designating one of a plurality of structures as a reference structure and remaining structures as relative structures, searching for the relative structures from the reference structure, storing relative structures having a surface visible from the reference structure, and removing relative structures having an invisible surface; conducting selection and storage based on distance measurement by measuring the distance from the reference structure to each of the stored relative structures and removing relative structures positioned beyond a reference spot predetermined with reference to the reference structure; and calculating a ray propagation path by calculating the propagation path of the ray between the reference structure and each of the relative structures stored in said conducting selection and storage based on distance measurement.