A memory retaining unit (106) of a virtual machine handling system (10) retains a memory image (IMG) of a first computer (100). An update recording unit (203) records update information (UD) indicating a partial region of a memory image (IMG1) which is updated by the execution of a transferred virtual machine (VM) by a virtual machine execution unit (202) of a second computer (200). When receiving an undo request, a return unit (160) transmits partial data (PD) indicated by the update information (UD) from the second computer (200) to the first computer (100). A virtual machine execution unit (102) of the first computer (100) executes a continuing process of the virtual machine (VM) using the memory image (IMG) retained in the memory retaining unit (106) and the partial data (PD) received from the second computer (200).