The discovery of topological insulator has generated strong activities in the condensed matter and high-energy physics communities. A prominent property of a topological insulator is the existence of gapless surface states in the form of a Dirac Hamiltonian with momentum and spin directions locked with each other. If Fermi energy is within the bulk gap, it is easy to expect that some physical quantities or phenomena can be evaluated from an effective surface Hamiltonian. On the other hand, one may question if some physical quantities do not just rely on effective surface models. The response induced by an external magnetic field is one of the interesting topics with the above ambiguity. Generally, this perturbation to a system has an effective Zeeman field term, a vector potential term, and further contributions. We particularly interested in the surface current induced by a static Zeeman/exchange field. This surface current can be related to the orbital magnetization of the system. Our results are consistent with the claim that orbital magnetization is a bulk property.