Abstract: A light emitting device includes a light source and a wavelength converter that includes a resin including a constitutional unit that includes an ionic liquid or a derivative of the ionic liquid, and a semiconductor nanoparticle phosphor included in the resin and provided on at least a portion of the light source. A wavelength converter includes a resin including a constitutional unit that includes an ionic liquid or a derivative of the ionic liquid, and a semiconductor nanoparticle phosphor included in the resin and emitting fluorescence upon receiving excitation light. A light emitting device includes the wavelength converter and a light source emitting excitation light to the wavelength converter, which is provided separately from the wavelength converter.