A synchronization signal detecting section is internally provided with a stream type counter for counting stream type information output from a header information analyzer and a stream type determining section for instructing, based on a value in the stream type counter, a signal processing section to initiate stream conversion. If the value in the stream type counter reaches a predetermined value, it is determined that the input signal is a stream signal. If the value in the stream type counter does not reach the predetermined value, synchronization signal detection is restarted from the address which is one bit ahead of an address stored in a synchronization address storing section.