A 3D measurement system of a tunnel shape is being developed. This system is composed of a mobile robot equipped with a 2D laser scanner and a three-axis fiber optic gyro, integrated software, and a total station placed in the tunnel. Measured data by the robot is transformed to the tunnel's coordinates system using the position information measured by the total station and the optic gyro. The integrated software is able to load the design data of 3D CAD system via LandXML format, and compare with the measured data. The error of the measured data is displayed in the software interface on-site. This paper describes the basic system architecture and the results of the measuring experiments in a simulated tunnel.