We present a new exact inflationary solution to nonminimally coupled scalar field. The inflation is driven by the evolution of scalar field with inflation potential V() = λ/4()4 - 1/2m2()2 + Vo. This includes the solution that behaves exponential inflation for ()o ＞ () ＞ ()end and then develops smoothly towards radiation-like evolution for () ＜ (()end. The spectral index of the scalar density fluctuations, ns, is computed, and the result is consistent with the analysis of the Wilkinson-microwave anisotropy probe data. This model can lead to successful inflation with λ≈ 10-7, rather than 10-13 reported previously.