A wavelength converter comprising: a substrate portion ; and an optical conversion layer including optical conversion inorganic particles and an inorganic binder portion that mutually holds the optical conversion inorganic particles , and being formed on the substrate portion , wherein the inorganic binder portion includes: an amorphous binder ; and granular binder particulates with an average particle size smaller than an average particle size of the optical conversion inorganic particles , and wherein, in a case where, in the optical conversion layer , a portion present close to the substrate portion with respect to an intermediate plane in a thickness direction of the optical conversion layer is defined as a substrate-side portion , and a portion present remote from the substrate portion with respect to the intermediate plane is defined as a non-substrate-side portion , when a ratio of an average volume concentration of the binder particulates in the substrate-side portion with respect to an average volume concentration of the optical conversion inorganic particles in the substrate-side portion is defined as a substrate-side binder particulate concentration ratio RFs and, when a ratio of an average volume concentration of the binder particulates in the non-substrate-side portion with respect to an average volume concentration of the optical conversion inorganic particles in the non-substrate-side portion is defined as a non-substrate-side binder particulate concentration ratio RFo, the substrate-side binder particulate concentration ratio RF S is larger than the non-substrate-side binder particulate concentration ratio RFo. a substrate portion ; and an optical conversion layer including optical conversion inorganic particles and an inorganic binder portion that mutually holds the optical conversion inorganic particles , and being formed on the substrate portion , wherein the inorganic binder portion includes: an amorphous binder ; and granular binder particulates with an average particle size smaller than an average particle size of the optical conversion inorganic particles , and wherein, in a case where, in the optical conversion layer , a portion present close to the substrate portion with respect to an intermediate plane in a thickness direction of the optical conversion layer is defined as a substrate-side portion , and a portion present remote from the substrate portion with respect to the intermediate plane is defined as a non-substrate-side portion , when a ratio of an average volume concentration of the binder particulates in the substrate-side portion with respect to an average volume concentration of the optical conversion inorganic particles in the substrate-side portion is defined as a substrate-side binder particulate concentration ratio RFs and, when a ratio of an average volume concentration of the binder particulates in the non-substrate-side portion with respect to an average volume concentration of the optical conversion inorganic particles in the non-substrate-side portion is defined as a non-substrate-side binder particulate concentration ratio RFo, the substrate-side binder particulate concentration ratio RF S is larger than the non-substrate-side binder particulate concentration ratio RFo. <EOS>