PURPOSE: To restrict the lateral oscillation and improve the withstand load property by supporting an upper structure with oscillation absorbing mechanisms on a main hull, and providing a longitudinal pair of lateral movement restriction type guide mechanisms and a bilateral pair of longitudinal oscillation restriction type guide mechanisms in the central part.

CONSTITUTION: An upper structure 2 is supported by oscillation absorbing mechanisms which consists of hydraulic cylinders 4, 5 at two positions in front and rear on a main hull 1. Guide frames 6, 6 are hanged in front and rear of the upper structure 2 to form lateral movement restriction type guide mechanisms in which tires 8, 8, of which vertical movement is allowed and the relative lateral movement is restricted with the guide frames 6, 6, are provided on the main hull 1. A pair of guide frames 7, 7 are provided in right and left of the central part of the upper structure 2 to form longitudinal movement restriction type guide mechanisms for guiding a tire 8' provided in the main hull 1 side so as to restrict the longitudinal movement thereof and allow the lateral oscillation and the vertical oscillation thereof. With this structure, the oscillation is restricted and a vessel can withstand a large load.