The hardware information showing a type of hardware constituting the computer resource and the software information showing a type of software mounted in the computer resource are stored in the entry corresponding to each computer resource in the computer configuration table managed by a management computer. Further, when a computer resource allocated to a certain job is determined, a computer resource which may be used for the job in the aftertime is selected with reference to the hardware information and the software information, and the job name is registered as a tentatively booked job name in the entry corresponding to the selected computer resource in the computer configuration table. When additionally allocating the computer resource, the computer resource which is tentatively booked is selected with priority, and the computer resource tentatively booked to another job is excluded from the additional allocation.