The transition probability of multiphoton processes strongly depends on the angle between the directions of the spin quantization and the magnetic field to induce the transitions. The rotary saturation method in NMR is an excellent one to observe the multiphoton processes in solids. In this paper, the experimental observation of the multiphoton transitions between the nuclear spin Zeeman levels of F nuclei in a CaF2 single crystal by the rotary saturation method is reported. Results are discussed by using a second quantization formalism and the nth order time-dependent perturbation theory in the doubly rotating frame.