Abstract: As a common device to limit the passing-through area of a light beam, apertures are widely used in optics and optical radiation measurement. In order to precisely measure the aperture area, metrology institutes around the world have done a lot of research. In this paper, an effective-aperture-area measurement facility based on a two-dimensional scanning method is established and the area of a circular aperture with a diameter of 8 mm is measured using the facility. The factors affecting the area measurement are analyzed, including the stability of the laser power, the signal fluctuation near the edge of the aperture, the speckle of the integrating sphere, and the uniformity of the inner wall. The experimental results showed that the relative extended uncertainty of the measured effective aperture area was 1.8×10⁻⁴ (k=2).