Effective superpotential and partial breaking of N=2 supersymmetry

We consider the effective superpotential of N=2, U(N) gauge model where N=2 supersymmetry is spontaneously broken to N=1. By the computation of loop diagrams, we obtain a formula for the effective superpotential which is deformed from the well-known form of the effective superpotential of N=1, U(N) gauge model with a tree level superpotential.