  We investigate the scalar induced gravitational waves (SIGWs) in the
Chern-Simons (CS) modified gravity during the radiation dominated era. The
SIGWs are circularly polarized, which provide us a tool to test the possible
parity violation in the early universe. We derive the semianalytic expressions
to evaluate the fractional energy density of the SIGWs, $\Omega_{\mathrm{GW}}$,
which receives contributions from the general relativity (GR) and the
correction due to the parity-violating term, respectively. We find that the
degree of the circular polarization of the SIGWs can be as large as of order
unity, although the contribution to $\Omega_{\mathrm{GW}}$ from the CS term is
at most of the same order as that from the GR.
