The present disclosure enables to accurately extract a signal derived from a tumor cell from data in which a signal derived from a non-tumor cell is mixed. According to an aspect of the present invention, there is provided a data processing method executed by a data processing apparatus including a processor. The data processing method including causing the processor to execute: an input step of inputting first DNA profile data obtained by measuring a sample including a tumor cell and a plurality of known non-tumor cells; a signal removal step of removing a signal derived from the non-tumor cell, which is mixed in the input first DNA profile data, to acquire only a signal derived from the tumor cell; and an output step of outputting the signal derived from the tumor cell as a DNA profile feature amount of the sample.