  We consider the Grover walk on infinite trees from the view point of spectral
analysis. From the previous works, infinite regular trees provide localization.
In this paper, we give the complete characterization of the eigenspace of this
Grover walk, which involves localization of its behavior and recovers the
previous works. Our result suggests that the Grover walk on infinite trees may
be regarded as a limit of the quantum walk induced by the isotropic random walk
with the Dirichlet boundary condition at the $n$-th depth rather than one with
the Neumann boundary condition.
