Temperature-dependent infrared photoreflectance (PR) is employed on InSb for clarifying resonant levels (RLs) and band edge structure. Abundant PR features are well resolved around the bandgap and are verified to be of electronic inter-level transitions rather than the Franz-Keldysh oscillations. The evolution of the critical energies with temperature reveals the nature of the PR processes, from which one acceptor RL, two donor RLs, and a shallow acceptor level are quantitatively identified, and a detailed band edge structure is derived. The results show that temperature-dependent infrared PR analysis can serve as an efficient vehicle for clarifying both bound and resonant levels in semiconductors.