A computer system includes: a physical resource including a memory; a virtualization mechanism that provides a virtual computer to which the physical resource is allocated; and a cache state management mechanism that manages a cache state of the virtual computer. The virtualization mechanism provides a first virtual computer and a second virtual computer. The cache state management mechanism manages the cache state of each of the first virtual computer and the second virtual computer. When the cache state management mechanism detects transition of the cache state in a state where a memory area allocated to a cache of the first virtual computer and a memory area allocated to a cache of the second virtual computer include duplicated areas storing same data, the virtualization mechanism releases the duplicated area in one of the first virtual computer and the second virtual computer.