In a lighting unit (UT1) of the present invention comprising a light
guiding plate (3), casings (5, 6) covering at least a pair of side
portions and a lower surface 3f of the light guiding plate so as to form
a column-shaped light source unit storage space (103) along a side
surface (3a) of one of the side portions, a reflecting sheet (4) disposed
between the lower surface of the light guiding plate and a bottom surface
of the casing such that an end (4a) thereof protrudes into the light
source unit storage space, and a light source unit (L) inserted into the
light source unit storage space and having a light source (1), a
reflector (2), and a light source holding component (7), wherein the
light source is bar-shaped and disposed along the side surface (3a) of
the light guiding plate, the reflector is plate-shaped and encloses the
side surface (3a) of the light guiding plate such that the light source
is located inside thereof and one end thereof is located under the end
(4a) of the reflecting sheet, and the light source holding component is
disposed on the reflector for holding both the end portions of the light
source, a structure (A) for inhibiting the end (2a) of the reflector from
entering between the light guiding plate and the reflecting sheet when
the light source unit is inserted into the light source unit storage
space or for confirming whether or not the end of the reflector has
entered is provided.