A wavelength converting device includes a diffused-reflecting layer, a substrate, and a photoluminescence layer. The diffused-reflecting layer has a first surface and a second surface facing away from the first surface, and the diffused-reflecting layer includes a hydrophilic binder and a lipophilic binder. The substrate is on the first surface of the diffused-reflecting layer. The photoluminescence layer is on the second surface of the diffused-reflecting layer.