  We review our recent studies on the Kondo effect in the tunneling phenomena
through quantum dot systems. Numerical methods to calculate reliable tunneling
conductance are developed. In the first place, a case in which electrons of odd
number occupy the dot is studied, and experimental results are analyzed based
on the calculated result. Tunneling anomaly in the even-number-electron
occupation case, which is recently observed in experiment and is ascribed to
the Kondo effect in the spin singlet-triplet cross over transition region, is
also examined theoretically.
