To shorten the process period for adjusting the center of gravity effectively and reduce the works for the hull as much as practicable.

The hull center-of-gravity adjusting device is composed of a plurality of structural sections to form the hull 1 and a piping 3 to connect one or more sections 2 to an opening 4 which is open at the side of the hull 1. The piping 3 is located in the design position to be specified when the structural sections are arranged, and the hull center-of-gravity adjusting material is introduced to the specific section(s) through the piping 3. The pipe laying is designed when the hull is designed, and the works for pipe laying are substantially completed when an inclination test at the center-of-gravity adjusting stage is to be conducted. The appropriate timing to conduct the inclination test is decided as early as at the design stage, and the time of delivery is decided well planned, and there is no need to execute works forcedly merely for adjustment of the center of gravity unreasonably in accordance with the delivery timing, which should shorten the construction period.