The invention relates to a power generation device for a revolving body underwater vehicle. Four power generators are fixedly arranged on a cross-shaped support frame; a pendulum hammer is positioned below the center of the cross-shaped support frame; and the pendulum motion of the pendulum hammer is converted into rectilinear motion of each threaded sleeve through four sets of spatial crank slider mechanisms composed of a top rod, a connecting rod and a threaded sleeve respectively. When each threaded sleeve rectilinearly moves, rotor shafts of the power generators are driven to rotate under the constraint of a guide rod and through the transmission of a reverse ball screw so as to realize the purpose of converting collected mechanical energy into electric energy for the use of the revolving body underwater vehicle. The power generation device has the beneficial effects that the shaking kinetic energy of the pendulum hammer in a space in different directions is converted into the electric energy, so that the problem of energy supply of the revolving body underwater vehicle is basically solved; the power generation device has the advantages of simple structure, easiness in processing and high efficiency; and the whole power generation device is cylindrical in appearance, is compact in structure, is installed in the revolving body underwater vehicle as an independent module, has the replaceability, is not affected by the marine bad environment and is not limited by power generation time.