To provide a mooring device and its installation method capable of mooring a floating body with small-sized cushioning members, being easily designed, and dispensing with a supporting chain.

In this mooring device where at least a pair of cushioning members 1A, 1B, 1C, 1D are mounted around a dolphin 21, each cushioning member is fixed to the floating body at its one end, and has the frames 2A, 2B, 2C, 2D opposite to the dolphin 21 at the other end, the frames are slidable with the dolphin, and the frames in the pair of cushioning member are connected to annularly surrounding the dolphin, when one of the cushioning members is compressed, the other cushioning member simultaneously produces the tension or the shearing, whereby all of cushioning members can effectively be used by utilizing the tensile reaction force and the shearing reaction force.