This invention provides a fuel tank of a simple structure without any special device but having space of a predetermined ratio after the fuel tank has been filled with liquefied fuel. The fuel tank is of a form in which a number of cylindrical or spherical containers are arranged in parallel and are coupled together in a manner that the cylindrical or spherical containers neighboring each other share partitioning walls, respectively. Each of the partitioning walls has a passage through which the neighboring cylindrical or spherical containers are communicated with each other, and the upper ends of the passages are formed leaving partly the inner partitioning walls so that the liquid will not enter into the upper parts of the cylindrical or spherical containers.
