  We deal with the Hill's spherical vortex, which is an exact solution to the
Euler equation, and manage the solution to satisfy the incompressible
Navier-Stokes(INS) equations with a viscous term. Once we get a viscous
solution to the INS equations, we will be able to analyze the flows with
discontinuities in vorticity.
  In the same procedure, we also present a time developing exact solution to
the INS equations, which has a rotation on the axis besides the Hill's vortex.
