  The pseudogap phenomena induced by the SC fluctuation are investigated in
details. We perform a calculation beyond the 1-loop approximation. The SC
fluctuation is microscopically derived on the basis of the repulsive Hubbard
model. The vertex corrections are collected in the infinite order with use of
the quasi-static approximation. The single-particle excitations, NMR 1/T_{1}T,
spin susceptibility and superconducting transition temperature are discussed.
The important role of the vertex correction is pointed out for the single
particle spectral function. On the other hand, the validity of the 1-loop order
theory is confirmed for other quantities. We shed light on the essential nature
of SC fluctuation leading to the pseudogap from the comparison with spin and
charge fluctuations.
