A device in a wireless communication system configured to support a cloud storage service, the device comprising: a transmitter; a receiver; and at least one processor, said at least one processor is configured to: acquire a shared address of at least one file in a cloud storage server upon detecting that the at least one file needs to be backed up, determine at least one other cloud storage server to which the at least one file will be backed up, adjust a timing point at which a backup request message is transmitted to the at least one other cloud storage server based on a speed at which the at least one other cloud storage server downloads a file, control the transmitter to transmit, based on the adjusted timing point, the backup request message comprising the shared address to the at least one other cloud storage server to back up the at least one file from the cloud storage server, control the transmitter to transmit, after transmitting the backup request message to the at least one other cloud storage server, a file state check request message to the at least one other cloud storage server in order to check a transmission state for the at least one file, receive, via the receiver, a file state check response message as a response message to the file state check request message from the at least one other cloud storage server, determine a file transmission state for the at least one file based on the file state check response message, and control the transmitter to transmit a file delete request message for requesting to delete the at least one file to the cloud storage server upon the user device detecting that the at least one other cloud storage server has completed download for the at least one file. a transmitter; a receiver; and at least one processor, said at least one processor is configured to: acquire a shared address of at least one file in a cloud storage server upon detecting that the at least one file needs to be backed up, determine at least one other cloud storage server to which the at least one file will be backed up, adjust a timing point at which a backup request message is transmitted to the at least one other cloud storage server based on a speed at which the at least one other cloud storage server downloads a file, control the transmitter to transmit, based on the adjusted timing point, the backup request message comprising the shared address to the at least one other cloud storage server to back up the at least one file from the cloud storage server, control the transmitter to transmit, after transmitting the backup request message to the at least one other cloud storage server, a file state check request message to the at least one other cloud storage server in order to check a transmission state for the at least one file, receive, via the receiver, a file state check response message as a response message to the file state check request message from the at least one other cloud storage server, determine a file transmission state for the at least one file based on the file state check response message, and control the transmitter to transmit a file delete request message for requesting to delete the at least one file to the cloud storage server upon the user device detecting that the at least one other cloud storage server has completed download for the at least one file. acquire a shared address of at least one file in a cloud storage server upon detecting that the at least one file needs to be backed up, determine at least one other cloud storage server to which the at least one file will be backed up, adjust a timing point at which a backup request message is transmitted to the at least one other cloud storage server based on a speed at which the at least one other cloud storage server downloads a file, control the transmitter to transmit, based on the adjusted timing point, the backup request message comprising the shared address to the at least one other cloud storage server to back up the at least one file from the cloud storage server, control the transmitter to transmit, after transmitting the backup request message to the at least one other cloud storage server, a file state check request message to the at least one other cloud storage server in order to check a transmission state for the at least one file, receive, via the receiver, a file state check response message as a response message to the file state check request message from the at least one other cloud storage server, determine a file transmission state for the at least one file based on the file state check response message, and control the transmitter to transmit a file delete request message for requesting to delete the at least one file to the cloud storage server upon the user device detecting that the at least one other cloud storage server has completed download for the at least one file.