A thin client system comprises a plurality of virtual desktop environment servers each including a virtual desktop environment in which a workplace environment is generated in a virtual machine, and a management server which manages setting of the virtual desktop environment and the virtual desktop environment server, wherein the management server comprises an OS sorting unit which generates information of an OS sorting result obtained by sorting the virtual desktop environment servers in the order of failing to have a virtual machine whose OS is other than OS of a virtual machine to be newly created, and a VM creating unit which determines the virtual desktop environment server in which the virtual machine is to be created based on the OS sorting result information by giving preference to the virtual desktop environment server failing to have a virtual machine having that other OS.