An illuminating device comprises one or more luminescent devices (1). The luminescent device comprises a semiconductor light emitting element (10) emitting a excitation light having an peak within a wavelength range from 350 nm to 430 nm, and a luminescent part (20) comprising a sealing member (22) and a phosphor (21) absorbing the light from the semiconductor light emitting element (10) and emitting a light with different emission spectrum. For the luminescent device (1), an excitation light contribution degree ΔE, an index quantitatively representing what extent of a visible component of the excitation light is involved in color mixing of a combined light of the luminescent device (1), is 0.005 or less, and a mean color rendering index Ra is 70 or more.