  We investigate effects of field theory instantons by considering D-instantons
in a suitable D3-brane background. In supersymmetric QCD with SU(N_c) gauge
group with N_f=N_c flavors, the moduli space of vacua is deformed by
instantons. This effect can be described by the chiral interactions which are
called multi-fermion F-terms. We derive these chiral interaction terms as
D-instanton effects in the presence of D3-branes. For SU(2), the obtained
result agrees with the previous result worked out by Beasley and Witten
[hep-th/0409149]. We also explicitly work out those for the case of the
symplectic gauge group, and show that they describe the deformation of the
moduli space.
