A parafermionic realization of the Kazama-Suzuki model is studied to derive vertex operators of NS chiral, R chiral and NS anti-chiral primary fields. For the derivation we employ the constraint with respect to the supercurrents G(z) and G(z) and postulate a “physical states conditions” by means of screening operators. It is found that a non-vanishing Yukawa coupling of the vertex operators satisfies a condition which includes a U(1) charge conservation law pointed out in the previous study.