Illumination device

A luminaire characterized in comprising a discharge lamp (1), a lighting device (62a) for supplying a power for lighting the discharge lamp, an igniter (62a') for starting the discharge lamp, and a lamp body (52j) provided at least with a discharge lamp holding member (3) and housing the discharge lamp, wherein the lighting device (62a) and igniter (62a') are provided as separated, the lighting device (62a) is provided in the lamp body (52j), and the igniter (62a') is provided adjacent to the discharge lamp, whereby said lamp body (52j) has a circular opening (521j) on the rear side of the lamp (1), said circular opening being provided with grooves; a lighting unit (6j) is provided to includes a block member (61j) and the lighting device (62a), said block member (61j) being shaped for blocking said circular opening (521j), said block member (61j) being shaped into a box shape having with a flange (616j) around a front opening thereof and having a plurality of bent projections (617j) extending from the base of said flange (616j), said lighting unit (6j) being fitted as rotated into said circuit opening (521j) of the lamp body (52j) with said bent projections (617j) inserted into grooves of said openings.