The invention relates to a respiratory motion detection apparatus (1) for detecting respiratory motion of a person. An illuminator (3) illuminates the person (2) with an illumination pattern (11), and a detector (4) detects the illumination pattern (11) on the person (2) over time. A temporal respiratory motion signal being indicative of the respiratory motion of the person (2) is determined from the detected illumination pattern by a respiratory motion signal determination unit (5). The illumination pattern deforms significantly with slight movements of the person. Thus, since the respiratory motion signal determination unit (5) is adapted to determine the temporal respiratory motion signal from the detected illumination pattern, even slight respiratory movements of the person can be determined. The sensitivity of detecting respiratory movements of a person can therefore be improved.