A light emitting device assembly includes: a light emitting device; and a light output member provided on the light emitting element and having an upper surface on which a curved part that outputs light from the light emitting device is provided, wherein a value of a x coordinate of a curved part center axis is a positive value, a locus of an edge of a curved part forms a circle or oval around the curved part center axis, light on a Z-axis output from an origin is output from the curved part at an angle θ0 (θ0>0) formed with the Z-axis within a XZ-plane, and function F(φ,Δφ) expressed by F(φ,Δφ)=(Δθ+−Δθ−)/Δφ  (1) monotonously increases, takes the maximum value at φ=φ0 (