  In 2D XY ferromagnet the dipole force induces a strong interaction between
spin-waves in the long-wavelength limit. The major effect of this interaction
is the transformation of a propagating spin-wave into a diffusion mode. We
study the anomalous dynamics of such diffusion modes. We find that the
Janssen-De Dominics functional, which governs this dynamics, approaches the
non-Gaussian fixed-point. A spin-wave propagates by an anomalous anisotropic
diffusion with the dispersion relation: $i\omega{\sim}k_{y}^{\Delta_y}$ and
$i\omega{\sim}k_{x}^{\Delta_x}$, where ${\Delta_y}=47/27$ and
${\Delta_x}=47/36$. The low-frequency response to the external magnetic field
is found.
