To provide an illuminating device having such a characteristic that lighting becomes dark and a color temperature is also reduced, only by increasing or decreasing brightness of each LED.

In an illuminating device 10, four LEDs with a color temperature of 3500K are serially connected as first LEDs 25, and four single-color LEDs of a peak wavelength of 600 nm are serially connected as second LEDs 26. A light control part 31 of an LED lighting device 10a controls a first constant current output circuit 17a so that the first LEDs 25 are turned on at an optical output according to a light control degree L, when receiving light control signals commanding a light control degree L[%] (5≤L≤100) from a light controller 32. At that time, the light control part 31 controls a second constant current output circuit 17b so that the second LEDs 26 are turned on at a constant optical output regardless of the light control degree L. A change rate of the optical output of the first LEDs 25 is constant regardless of magnitude of the light control degree.