  The present work is a study of the unitarity problem for Quantum Mechanics at
Planck Scale considered as Quantum Mechanics with Fundamental Length (QMFL).In
the process QMFL is described as deformation of a well-known Quantum Mechanics
(QM). Similar to previous works of the author, the basic approach is based on
deformation of the density matrix (density pro-matrix) with concurrent
development of the wave function deformation in the respective Schrodinger
picture. It is demonstrated that the existence of black holes in the suggested
approach in the end twice results in nonunitary transitions (first after the
Big Bang of QMFL to QM, and then when on trapping of the matter into the black
hole the situation is just the opposite - from QM to QMFL)and hence in recovery
of the unitarity. In parallel this problem is considered in the deformation
terms of Heisenberg algebra, showing the identity of the basic results. From
this an explicit solution for Hawking's informaion paradox has been derived
