Superconducting critical phenomena in the whole temperature range, including the region below Tc, are investigated with the aid of the functional integral representation of superconductivity. Particularly, in the critical range, where the mean field theoretical approach for interacting fluctuation modes breaks down, the one-particle Green's function, i.e., the fluctuation propagator, is examined by the dimensional analysis method, and the shift of the transition temperature from that defined by the BCS theory is obtained. Further an excess conductivity in this range is shown to saturate to the value of the order of the normal-state conductivity irrespective of the dimensionality of specimen, except for in the very narrow range near the shifted transition temperature Tc. Characteristic aspects of fluctuations just at and below Tc are also investigated, and, in particular, a mechanism for intrinsic resistivity below Tc due to thermally activated processes of fluctuations is conjectured even in a two-dimensional superconductor. The microscopic justification of the functional integral method, which is just the Ginzburg-Landau theoretical scheme, is also given.