  We construct a supersymmetric grand unified model in which a dynamical
symmetry breaking of SU(5)$_{GUT}$ generates large masses for color-triplet
Higgs multiplets while keeping SU(2)$_L$-doublet Higgs multiplets naturally
light. The vanishing masses for the Higgs doublets are guaranteed by the
Peccei-Quinn symmetry. We also show that the Peccei-Quinn symmetry suppresses
the dangerous dimension 5 operators for the nucleon decay.
