A wavelength conversion element includes an illumination system, a light valve, and a projection lens. The illumination system is configured to provide an illumination beam. The light valve is disposed on a transmissive path of the illumination beam to convert the illumination beam into an image beam. The projection lens is disposed on a transmissive path of the image beam. The illumination system includes an excitation beam source and the aforementioned wavelength conversion element. The excitation beam source is configured to provide an excitation beam. The wavelength conversion element is disposed on a transmissive path of the excitation beam. A projection apparatus adopting the aforementioned wavelength conversion element is further provided. The substrate has good structural strength and the surface of the substrate has better flatness, so the excitation beam can be accurately focused on the wavelength conversion layer to maintain stable excitation efficiency.