The second order nonlinearity of C60 was deduced from the Pockels response of a mixed C60/AA LB monolayer by using electrooptically modulated attenuated total reflection spectroscopy. The obtained considerable second order susceptibility of C60 χ(2)(-ω;ω,0)=0.5×10-12 m/V(i.e. 1.3×10-9 esu), in agreement with that obtained from the SHG measurement. And, the superpolarizability of C60, β=1.1×10-30 esu, was calculated using a monolayer model.