Micro/nano-combined hierarchical structures were fabricated by electron irradiation of polymer precursor film. When silicone grease film was irradiated with an electron beam, hierarchical pore structures were fabricated. Surfaces with hierarchical pore structures exhibited good superhydrophobic property after surface treatment with fluorosilane. However, large-area fabrication was difficult because the precursor material was highly viscous and thus large-area precursor with uniform thickness was hard to be prepared. As a method overcoming this limitation, precursor film was prepared by successive spin coating of PMMA colloidal solution and silicone grease diluted in hexane. After electron irradiation, the precursor film was converted to a polymer/ceramic composite film with the highly porous hierarchical structures consisting of micrometer-sized pores and microparticles decorated with nanobumps. The fabricated films with the hierarchical porous structure exhibit good superhydrophobicity with excellent self-cleaning and anti-adhesion properties after surface treatment with fluorosilane. In addition, the superhydrophobic coatings showed high hardness and strong adhesion to the substrate. The presented technique provides a straightforward route to produce large-area and mechanically robust superhydrophobic films on various substrate materials.