We propose a new dimensional measurement technique that is capable of measuring the bottom surface of a stepwise shape. The measurement system is composed of a length scale and a sensor probe to read the scale. The probe is trapped and controlled three-dimensionally by laser trapping technique. The scale is arisen by optical interference, which is extended straight to the measured surface from the probe. Firstly measurement principle is theoretically explained. Remarkable feature of this technique is feasibility to access the area as narrow as 15 μm. Vertical resolution of this measurement technique is experimentally estimated as 10 nm. The measurable range of the inclination angle of surface is less than 15°. In terms of the measurement accuracy, it is evaluated around 100 nm.