A gas turbine generator plant is provided in which, by forming auxiliary equipment, including a starter, a lubricating oil device, a control oil device, and a lubricating oil main tank, into a unit, the auxiliary equipment may be disposed with a building in a unitary manner with a generator and a gas turbine unit. The auxiliary equipment is made unitary to form the unitary auxiliary equipment. The unitary auxiliary equipment, the generator, and the gas turbine unit are disposed first, second, and third, respectively, within the building. Thus, the installed floor area of the plant may be dramatically reduced and in turn, construction costs may also be reduced. Furthermore, the unitary auxiliary equipment can be transported in one piece under a water resistant cover, so that it is possible to limit, all at once, the occurrence of rust on the unitary auxiliary equipment that could result from exposure to salt air during sea transport. The packing may also be high-density so as to reduce transportation costs. Furthermore, there are also few installation points to reduce installation costs. In addition, only a single dedicated crane need be installed to carry out the maintenance to further save costs.