Studying Structure of Electroweak Corrections

Several different effects in electroweak quantum corrections are explored separately through the latest data on the weak-boson masses. The leading-log approximation, the improved-Born approximation and the non-decoupling top-quark effects are studied without depending on the recent CDF data of $m_t$, and the results are given in a form independent of the Higgs mass. On the other hand, the bosonic- and the non-decoupling Higgs effects are examined by fully taking account of those CDF data. It is emphasized that future precision measurements of $M_W$ and $m_t$ are considerably significant not only for further studies of the electroweak theory at higher confidence level but also for new physics searches beyond it.