The present invention provides a method for playing contents, which are stored in a storage device connected via at least one interface, the method comprising: detecting a connection of the storage device; transmitting transaction information stored in the detected storage device to a license server, wherein the transaction information includes transaction identification information which identifies a corresponding transaction and a user; receiving, from the license server, license information allowing to play the contents; and playing the contents on the basis of the license information, wherein the license information includes a license file and a license key.