  We construct a supersymmetric composite model in type IIA T^6/(Z_2 x Z_2)
orientifold with intersecting D6-branes. Four generations of quarks and leptons
are naturally emerged as composite fields at low energies. Two pairs of light
electroweak Higgs doublets are also naturally obtained. The hierarchical Yukawa
couplings for the quark-lepton masses can be generated by the interplay between
the string-level higher dimensional interactions among "preons" and the
dynamics of the confinement of "preons". Besides having four generations of
quarks and leptons, the model is not realistic in some points: some exotic
particles, one additional U(1) gauge symmetry, no explicit mechanism for
supersymmetry breaking, and so on. This model is a toy model to illustrate a
new mechanism of dynamical generation of Yukawa couplings for the masses and
mixings of quarks and leptons.
