A noise processing apparatus measures a first potential difference signal, between a first electrode that is arrange at a location other than a steering unit in an apparatus and a second electrode that is used as a reference electrode, and measures a second potential difference signal, between the second electrode and a third electrode that is arranged on the steering unit in the apparatus. The noise processing apparatus calculates the intensities of the first potential difference signal and the second potential difference signal at predetermined intervals. The noise processing apparatus calculates the difference between the intensities of the first potential difference signal and the second potential difference signal calculated at the predetermined intervals. The noise processing apparatus corrects the first potential difference signal or the second potential difference signal at the predetermined intervals by using the calculated difference such that the intensities of the first potential difference signal and the second potential difference signal are canceled out. The noise processing apparatus calculates a differential signal indicating the difference between the first potential difference signal and the second potential difference signal at the predetermined intervals by using the corrected potential difference signal. The noise processing apparatus outputs the differential signal.
