In an electroluminescent device comprising an insulating substrate having consecutively thereon a first electrode, a first insulating layer, a luminescent layer composed of two types or more luminescent portions differing in luminescent color which are provided in a flat panel arrangement to give a single-layered luminescent layer, a second insulating layer and a second electrode, a first dielectric film is disposed between the luminescent portions to provide an isolation layer for isolating the luminescent portions, and a second dielectric film for adjusting the luminescence threshold voltage is disposed on the light outcoupling side or on the side opposite thereto of one of said luminescent portions. Herein, the first and second dielectric films provided for isolating the luminescent portions and for adjusting the luminescence threshold voltage, respectively, are made of the same material and have a refractive index lower than that of both luminescent portions.