Abstract: The present invention has an object to reduce the manufacturing cost of a power supply substrate connected to a discharge tube in an illuminating device by reducing the size of the power supply substrate. The illuminating device 2 according to the present invention includes a chassis 4, discharge tubes 20 which have electrodes 17 at respective end portions of glass tubes 18 and in which the glass tubes 18 are bent such that these electrodes 17 are disposed in one direction, and a power supply substrate which supplies power to the discharge tubes 20. Two discharge tubes 20 are disposed inside the chassis 4. The discharge tubes 20 are housed side by side inside the chassis 4 such that the respective electrodes of the two discharge tubes 20 are lined up in one direction when the chassis 4 is seen in a plan view.