A new multi-hull-type floating wave energy converter, which consists of multi floating bodies with asymmetrical cross section and the bars connecting these bodies, is proposed and fundamental studies on this converter are conducted. Wave energy absorbed by this converter is induced from the motions of the floating bodies and the connecting bars in waves. The authors developed the method to calculate the hydrodynamic forces and moments acting on this converter by using Okusu method, in which the hydrodynamic interaction between the floating bodies are taken into account. Here they derived the equation of the motions of floating bodies and connecting bars in waves by balancing the hydrodynamic forces on floating bodies with the forces on connecting bars. For the twin-hull-type floating wave energy converter which consists of two salter duck type bodies and a connecting bar, hydrodynamic forces, motions, efficiencies of wave energy absorption etc. were calculated as model experiments were carried out. It is found that the results of calculation by this method are in agreement with the ones by model experiments and the twin-hull-type floating wave energy converter is capable of absorbing more stable wave energy than that of the single-hull-type.