  In 1954, G. P\'olya conjectured that the counting function of the eigenvalues
of the Laplace operator of Dirichlet (resp. Neumann) boundary value problem in
a bounded set $\Omega\subset{\mathbb R}^d$ is lesser (resp. greater) than $C_W
|\Omega| \lambda^{d/2}$. Here $\lambda$ is the spectral parameter, and $C_W$ is
the constant in the Weyl asymptotics. In 1961, P\'olya proved this conjecture
for tiling sets in the Dirichlet case, and for tiling sets under some
additional restrictions for the Neumann case. We prove the P\'olya conjecture
in the Neumann case for all tiling sets.
