In each work process of the assembly work of a large rotating machine, an input terminal unit 101 displays measuring points necessary for measurements of radial and axial clearances between a rotor and a casing so as to provide workers with instructions. When workers measure the clearances at the instructed measuring points, the measured values will be supplied to the input terminal unit 101 so as to confirm whether the measured values are within design tolerances or not. In addition, when workers measure the clearances at the instructed measuring points, amounts of adjustment of the casing will be displayed so that the measurement results at the measuring positions will have an optimum positional relation with the designed values.