This paper presents a measurement system for 3-D microstructures that uses an optical fiber probe equipped with a piezo element that causes the probe to vibrate. The optical fiber probe consists of a stylus shaft with a diameter of 3 μm and a glass ball with a diameter of 5 μm attached to the tip. The stylus is set such that it moves in a circular motion in a plane. The measurement principle involves the monitoring of the vibrational amplitude of the stylus that is required to prevent adhesion of the stylus tip onto the measured surface caused by the surface force, and this amplitude is measured optically. In this study, the stylus characteristics are examined. The effects of the relative humidity and the surface roughness on the surface force are then evaluated. As a result, it is shown that the surface force increases significantly when the relative humidity is greater than 40%, and there is no adhesion of the stylus tip to the measured surface due to the surface force when the stylus vibrational amplitude is greater than 0.5 μm. In addition, there is no surface roughness effect on the surface force between 0.2 μm and 0.8 μm.