A near-field scanning optical microscope is disclosed. The microscope includes a lighting component, a probe and an ellipsoidal mirror. The lighting component emits a light. The probe is disposed on one side of a testing sample, and the light is focused around a probe tip to draw the near-field light out. The ellipsoidal mirror has a first focal point and a second focal point, and the first focal point and the probe tip are disposed at the corresponding positions, and the near-field light drawn out from the probe tip is scattered from the first focal point inside the ellipsoidal mirror, and reflected and passed through the second focal point.