  The Lorentz transformation properties of the equal-time bound-state
Bethe-Salpeter amplitude in the two-dimensional massless quantum
electrodynamics (the so called Schwinger Model) are considered. It is shown
that while boosting a bound state (a `meson') this amplitude is subject to
approximate Lorentz contraction. The effect is exact for large separations of
constituent particles (`quarks'), while for small distances the deviation is
more significant. For this phenomenon to appear, the full} function, i.e. with
the inclusion of all instanton contributions has to be considered. The
amplitude in each separate topological sector does not exhibit such properties.
