As the Phase II project of “Research & Development of Huge Floating Offshore Platform” carried out by the Mega-Float Technological Association, the proto-type of floating airport using the large floating platform (1000m in length, maximum 120m in breadth and 3m in depth) was installed at the Tokyo Bay in 1999. The model of floating airport consists of mainly 3 floating units with runway such as A, B and C. They were constructed at different shipping yards and connected together on the sea. A and C unit for runway have been constructed at shipping yard in the Ise Bay and B unit has been done in the Tokyo Bay. There are very few data concerning the full-scale measurement of such a flat structure with small depth. However, there is a possibility of the occurrence of various kinds of structures in the future for the development of the ocean space utilization. Transportation by towing has been one of the conventional way of techniques from old times, the limitation of experiment however exists because of its big size. The accumulation of full-scale data is quite important especially in the long distance towing of huge floating structure like Mega-Float unit in the outer ocean. Authors made a full-scale measurement using the floating unit (100m in length, 60m in breadth and 2m in depth) in the phase I project as well as the model experiment in the basin. The towing force and strain on the upper-deck etc. have been measured in both experiments. A floating unit constructed in the phase II project is the same size as the completed structure in the phase I project. The towing force and structural strength of the floating unit have been discussed in this paper.