A digital broadcast receiver and an upgrading method thereof that can achieve an upgrade stabilization. The digital broadcast receiver includes a tuner to receive broadcast data of a selected channel, a demultiplexer to separate new middleware data and information data corresponding to the new middleware data from the broadcast data, a memory to pre-store previous middleware data and to store the new middleware data and the information data, and a controller to determine whether to store the new middleware data in the memory based on the information data. If storage of the new middleware data is completed, the controller checks whether an upgrade is successful by executing the new middleware data, and if the upgrade fails, the controller executes the previous middleware data pre-stored in the memory. Thus, the receiver upgrades the received middleware program in a stable manner.