  The tension between recent observations and theories on cosmic ray (CR)
diffusion necessitates exploration of new CR diffusion mechanisms. We perform
the first numerical study on the mirror diffusion of CRs that is recently
proposed by Lazarian & Xu (2021). We demonstrate that the perpendicular
superdiffusion of turbulent magnetic fields and magnetic mirroring that
naturally arise in magnetohydrodynamic (MHD) turbulence are the two essential
physical ingredients for the mirror diffusion to happen. In supersonic,
subsonic, and incompressible MHD turbulence, with the pitch angles of CRs
repeatedly crossing $90^\circ$ due to the mirror reflection, we find that the
mirror diffusion strongly enhances the confinement of CRs, and their
pitch-angle-dependent parallel mean free path can be much smaller than the
injection scale of turbulence. With the stochastic change of pitch angles due
to gyroresonant scattering, CRs stochastically undergo slow mirror diffusion at
relatively large pitch angles and fast scattering diffusion at smaller pitch
angles, resulting in a L\'{e}vy-flight-like propagation.
