A wavelength conversion element includes a base plate and a plurality of wavelength conversion layers. The base plate has a plurality of wavelength conversion regions. The plurality of wavelength conversion layers are respectively disposed on the wavelength conversion regions. The wavelength conversion layers are sintered and connected together. The invention also provides a projection device having the wavelength conversion element and a manufacturing method of the wavelength conversion element. The wavelength conversion element of the invention can have good conversion efficiency and long service life, so that the projection device with the wavelength conversion element can provide a good image quality.