1. A virtual computer system having a hypervisor that divides a physical computer into a plurality of logical partitions, that runs operating systems in the logical partitions, and that controls allocation of resources of said physical computer to the logical partitions, said virtual computer system comprising: a user interface through which one setting or a plurality of settings concerning the control actions of said virtual computer system is entered; a load measuring means for measuring loads, which are to be accomplished by the operating systems in the logical partitions, according to the settings entered through said user interface; and an adaptive control means for determining the allocation ratios of the computer resources relative to the logical partitions according to the settings entered through said user interface and the loads to be accomplished by the operating systems in the logical partitions which are measured by said load measuring means, and for when the determined allocation ratios are different from the previous ones, instructing said hypervisor to vary the allocation ratios, wherein: said hypervisor includes an allocation ratio varying means that dynamically varies the allocation ratios of the computer resources relative to the logical partitions in response to the instruction issued from said adaptive control means.