The diffusion of chaotic orbits in a widespread chaotic sea is normal
with a variance proportional to the time t even when islands of tori e
xist as long as there are no accelerator-mode islands. If an external
driving force is applied, however, the diffusion becomes anomalous wit
h a variance t(zeta), zeta > 1. Indeed, if one uses the coordinate sys
tem moving with the mean velocity of chaotic orbits due to the driving
force, the chaotic orbits become identical to the Levy flight due to
the intermittent sticking to the islands of tori. This is shown numeri
cally using the standard map with an external force, i.e., The Josephs
on map. The probability distribution function of the coarse-grained ve
locity is determined explicitly and turns out to obey an anomalous sca
ling law characterized by the exponent zeta.