In this note, we consider the Fourier integral operator with 𝑎 in the forbidden Hörmander class and satisfying the strong non-degeneracy condition. For , set When , and , we show that is bounded from the Besov space to . This result is a generalization of some theorems proved by Stein, Meyer, Runst and Bourdaud for the pseudo-differential operator with , and indices 𝑠 and are sharp in some cases.