  Diagrammatic analysis for normal state of Hubbard model proposed in our
previous paper [1] is generalized and used to investigate superconducting state
of this model. We use the notion of charge quantum number to describe the
irreducible Green's function of the superconducting state. As in the previous
paper we introduce the notion of tunneling Green's function and of its mass
operator. This last quantity turns out to be equal to correlation function of
the system. We proved the existence of exact relation between renormalized
one-particle propagator and thermodynamic potential which includes integration
over auxiliary interaction constant. The notion of skeleton diagrams of
propagator and vacuum kinds were introduced. These diagrams are constructed
from irreducible Green's functions and tunneling lines. Identity of this
functional to the thermodynamic potential has been proved and the stationarity
with respect to variation of the mass operator has been demonstrated.
