We consider the perturbed simple pendulum equation -u″(t) = μf(u(t)) + λsin u(t), t ∈ I: = (-T, T), u(t) > 0, t ∈ I, u(±T) = 0, where λ > 0 and μ ∈ R are parameters. The typical example of f is f(u) = u p-1u(p > 1). The purpose of this paper is to study the shape of the solutions when λ ≫ 1. More precisely, by using a variational approach, we show that there exist two types of solutions: one is almost flat inside I and another is like a step function with two steps.