A bus controller for controlling a bus communication system wherein each initiator of a plurality of initiators connected to a bus generates and sends a request signal to request use of the bus at predetermined intervals, and upon being granted use of the bus in response to the request signal, sends a command signal to instruct execution of a predetermined process to a target connected to the bus, and when the each initiator determines that the predetermined process is not to be executed by the target, the each initiator sends, upon being granted use of the bus again, the command signal to the target, the bus controller comprising: a bus control unit configured to, upon receiving the request signal from the each initiator, grant use of the bus to the each initiator based on predetermined priorities; and a mask generating unit configured to control a timing to be periodic at which the bus control unit grants use of the bus to at least one initiator, characterized in the mask generating unit comprising: a mask interval setting unit configured to set, as a mask interval, an interval for masking the request signal generated by the each initiator; a mask condition setting unit configured to set, as a plurality of mask conditions, a plurality of combinations of initiators to be subject to masking; and and initiator mask ID counter of an initiator mask ID corresponding to each of the plurality of mask conditions set by the mask condition setting unit, and wherein the mask generating unit, at each mask interval set by the mask interval setting unit, counts up the initiator mask ID counter, determines a selected initiator to be subject to masking among the plurality of initiators in correspondance to at least in part the value indicated by the initiator mask ID counter, and masks a request signal generated by the selected initiator. a bus control unit configured to, upon receiving the request signal from the each initiator, grant use of the bus to the each initiator based on predetermined priorities; and a mask generating unit configured to control a timing to be periodic at which the bus control unit grants use of the bus to at least one initiator, characterized in the mask generating unit comprising: a mask interval setting unit configured to set, as a mask interval, an interval for masking the request signal generated by the each initiator; a mask condition setting unit configured to set, as a plurality of mask conditions, a plurality of combinations of initiators to be subject to masking; and and initiator mask ID counter of an initiator mask ID corresponding to each of the plurality of mask conditions set by the mask condition setting unit, and a mask interval setting unit configured to set, as a mask interval, an interval for masking the request signal generated by the each initiator; a mask condition setting unit configured to set, as a plurality of mask conditions, a plurality of combinations of initiators to be subject to masking; and and initiator mask ID counter of an initiator mask ID corresponding to each of the plurality of mask conditions set by the mask condition setting unit, and wherein the mask generating unit, at each mask interval set by the mask interval setting unit, counts up the initiator mask ID counter, determines a selected initiator to be subject to masking among the plurality of initiators in correspondance to at least in part the value indicated by the initiator mask ID counter, and masks a request signal generated by the selected initiator.