  The dual Meissner effect is described and numerically observed in a
gauge-invariant way in lattice Monte-Carlo simulations of pure SU(2) QCD.
  A gauge-invariant Abelian-like field strength is defined in terms of a
unit-vector in color space which is constructed by a non-Abelian field strength
itself. A gauge-invariant monopole-like quantity is defined by a violation of
the Bianchi identity with respect to the Abelian-like field strength. The
squeezing of the non-Abelian electric field $\sqrt{\sum_a(E^a_i)^2}$ between a
pair of static quark and anti-quark occurs due to the solenoidal current coming
from the gauge-invariant monopole-like quantity. An equation similar to the
dual London equation is confirmed approximately in the long-range region.
