In this study, photonic crystals with a partial bandgap are demonstrated in the visible region using single-crystal diamonds. Quasi-three-dimensional photonic crystal structures are fabricated in the surface of the single-crystal diamonds using a tetrahedron Faraday cage that enables angled dry etching in three directions simultaneously. The reflection spectra can be controlled by varying the lattice constant of the photonic crystals. In addition, nitrogen-vacancy center single-photon sources are implanted on top of the diamond photonic crystals, and doubled collection efficiency from the light sources is achieved.