  We present the derivation of Hawking radiation by using the tunneling
mechanism in a rotating and charged black hole background. We show that the
4-dimensional Kerr-Newman metric, which has a spherically nonsymmetric
geometry, becomes an effectively 2-dimensional spherically symmetric metric by
using the technique of the dimensional reduction near the horizon. We can thus
readily apply the tunneling mechanism to the nonspherical Kerr and Kerr-Newman
metric.
