A lighting unit to be used for illumination includes an LED unit having a semiconductor light emitting unit, a radiating board for directly fixing the semiconductor light emitting unit to an upper surface, and a contact formed on the radiating board and serving to input a power to cause the semiconductor light emitting unit to emit a light, an attachment having a power supply portion for surrounding and holding the LED unit and supplying a power to cause the semiconductor light emitting unit to emit a light from an external power plug to the contact in a state in which at least a part of lower and side surfaces of the radiating board and an upper part of the semiconductor light emitting unit are open.