Provided are a light emitting element capable of maintaining high fluorescent intensity over a long period, and a fluorescent light source device. The light emitting element according to the present invention includes: a substrate; a reflection layer formed of a material containing Ag or Al, formed on the upper layer of the substrate; a diffusion prevention layer formed of a layer at least part of which being crystallized, the diffusion prevention layer being formed in contact with a surface of the reflection layer on a side opposite to the substrate; an enhanced reflection layer formed in contact with a surface of the diffusion prevention layer on a side opposite to the substrate; and a fluorescent body layer formed on the upper layer of the enhanced reflection layer.