The data processing device includes a virtual data sequence generator to extrapolate an approximate line approximating a temporal change of an input data sequence being inputted from outside and is a sequence of data at time points of a predetermined first number that are arranged in succession with at a predetermined time interval to a head or a tail of input data sequence and to generate a virtual data sequence being a sequence of data representing values on extrapolated approximate line at time points of a predetermined second number that are arranged in succession with the time interval, the time points including a time point being adjacent to input data sequence, a data sequence connector to generate a processed data sequence being a data sequence in which virtual data sequence is connected to input data sequence on a side where approximate line of input data sequence is extrapolated.