The disclosure provides a projection device with a wavelength conversion module including a ceramic substrate, a ceramic intermediate layer, a ceramic reflection layer, and a wavelength conversion layer. The ceramic reflection layer is disposed on the ceramic intermediate layer disposed on the ceramic substrate. The thermal expansion coefficient of the ceramic intermediate layer ranges from the thermal expansion coefficient of the ceramic substrate and the thermal expansion coefficient of the ceramic reflection layer. The wavelength conversion layer is disposed on the ceramic reflection layer. With the wavelength conversion module and the projection device, separation or gaps between the ceramic substrate and the ceramic reflection layer caused by a significant difference of the thermal expansion coefficients is prevented, the adhesion between the ceramic substrate and the ceramic reflection layer is further improved, the service life and the structural reliability of the wavelength conversion module are improved.