Abstract: Provided is a construction apparatus for safe and smooth construction of a floating offshore wind turbine generator in deep sea. The construction apparatus for constructing the offshore wind turbine generator with a crane ship includes a guide member attached to the crane ship in a work position perpendicular thereto such that a bottom end of the guide member is disposed under the sea and at least one pair of arm units that include grippers capable of holding and releasing a tower member divided into a plurality of segments in an axial direction and that slide along the guide member.