There is a master server according to an embodiment of the present invention that includes: a remote USB information manager receiving information on a USB device connected to a remote USB bridge from the remote USB bridge and managing the received information; a virtual machine information manager receiving information of a user's virtual machine from a virtual machine host server and managing the received information; a user request processor, in accordance with a request of a user who wants to access a predetermined USB device on the remote USB bridge, extracting information on the corresponding USB device from the remote USB information manager and extracting the information on the user's virtual machine from the virtual machine information manager; and a remote USB connection controller connecting the user's virtual machine to the predetermined USB device by using the information extracted by the user request processor.