  Motivated by future collider proposals that aim to measure the Higgs
properties precisely, we study the partial decay widths of the lightest Higgs
boson in the minimal supersymmetric standard model with an emphasis on the
parameter region where all superparticles and heavy Higgs bosons are not
accessible at the LHC. Taking account of phenomenological constraints such as
the Higgs mass, flavor constraints, vacuum stability, and perturbativity of
coupling constants up to the grand unification scale, we discuss how large the
deviations of the partial decay widths from the standard model predictions can
be. These constraints exclude large fraction of the parameter region where the
Higgs widths show significant deviation from the standard model predictions.
Nevertheless, even if superparticles and the heavy Higgses are out of the reach
of 14TeV LHC, the deviation may be large enough to be observed at future
$e^+e^-$ collider experiments.
