To provide a sound input/output processing method capable of realizing real-time sound multiple processing by dynamically changing processing priority according to processing contents of sound processing.

This method is provided with a sound processing priority table 104 storing a sound input/output processing object, sound data conversion priority, the presence of a real-time property and processing end information in a prescribed time by making them pairs and a priority control part 105 deciding whether or not the real-time sound multiplex processing is possible referring to the sound processing priority table 104 and deciding the processing priority capable of the real-time sound multiplex processing in addition to a sound data conversion part 101 and a sound data recording form storage table 102, etc.