A data processing apparatus which divides stream data into portions is disclosed. An evaluation value calculating section calculates an evaluation value at a dividing candidate position of the stream data based on an evaluation function. A comparing section compares the evaluation value calculated by the evaluation value calculating section with a predetermined threshold value. A dividing candidate position obtaining section obtains the dividing candidate position of the stream data in each predetermined unit. A controlling section decides a dividing position of the stream data based on a compared result of the comparing section. A controlling section causes the dividing candidate position obtaining section to obtain a second dividing candidate position when the compared result of the comparing section denotes that the evaluation value at the first dividing candidate position does not exceed the threshold value.