Provided is a bandwidth control method for a computer system that includes: at least one storage system; a plurality of host computers connected to the storage system via a network; and a management computer connected to the host computers, the method including the steps of: monitoring a state of the host computers; judging whether or not the each host computer is in a priority state in which operation of the host computer needs to be given priority over other host computers; communicating over a priority bandwidth when it is judged that the host computer is in a priority state; and communicating, when it is judged that the host computer is not in a priority state, over a non-priority bandwidth, which corresponds to one of a part and an entirety of a bandwidth remaining after allocating priority bandwidths to other host computers that are in a priority state.