Provided is an edge light type planar light source device capable of preventing luminance unevenness. An edge light type planar light source device (4) includes a light guide plate (7) emitting light entering from an end face (74) from a front face, a linear light source unit (11) including LED elements (111) including light emitting surfaces (113) and an LED substrate (112) where the elements are aligned, the surfaces opposed to the end face, a floor face (91) where the plate is disposed, and a locking member (10) erecting on the floor face and inserted in a peripheral portion of the plate from a back face toward the front face, wherein some elements are disposed in a vicinity of the locking member and are disposed on the substrate such that the surfaces are inclined toward the end face to gather the light at the rear of the locking member.