We systematically study geometries and band structures of two-dimensional group-V bilayer materials, i.e. phosphorene, arsenene and antimonene. Among the four stacking structures (AA, AB, AC, and AD), the AB stacking structures are found to be the largest band gaps and to be the most energetically stable. We find novel band structures on the whole Brillouin zone edges: four bands have close energies and two of the four bands have the same energy in many cases. We analyze the characteristic features of the band structures based on the group theory and clarify that the features depend on the space group of each stacking structure. We also find that the band splits due to the interlayer interaction is very small and this interaction becomes large as atoms become heavy.