A method and apparatus for processing streaming data of content in a digital broadcast system supporting Video On Demand (VOD) service are provided. A data processing method of a set-top box supporting Video On Demand (VOD) service includes requesting content selected by a user, configuring, if streaming data of the content is received, file block information for storing the streaming data, and storing the streaming data in units of file blocks according to the file block information. The streaming data processing method and apparatus of the present invention are capable of processing the streaming data of the content of which size is larger than the available storage space efficiently. Also, the streaming data processing method and apparatus of the present invention is capable of reducing total manufacturing cost of the set-top box by reducing costly storage device in size.