A lighting device comprising: a rod-shaped light guide extending in a longitudinal direction and having an end surface and a lateral surface, the light guide being configured to guide light entering from the end surface and emit linear light from the lateral surface; a light guide holder having a hole to receive the end surface of the light guide, and an opening optically communicating with the hole, the opening being formed in a first flat surface that is flat and opposite to a surface having the hole that receives the end surface of the light guide; a housing to house the light guide and the light guide holder and support the light guide holder with the end surface of the light guide exposed to an outside; the housing including a side wall, a light source base plate on which a light source element that emits light toward the end surface of the light guide is formed; and a base plate protection layer having a second flat surface that covers the light source base plate and is flat, the base plate protection layer being formed on a region of the light source base plate other than at least a region on which the light source element is formed, characterized in that: at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the housing with a bonding member therebetween or the at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the first flat surface of the light guide holder with the bonding member therebetween, at a position, in a direction along the longitudinal direction, at which the light emitted by the light source element enters the opening,and in a cross section intersecting with the longitudinal direction, the side wall is arranged between the light source base plate and the light guide holder in a region other than at least a portion at which the end surface of the light guide is exposed to the outside. a rod-shaped light guide extending in a longitudinal direction and having an end surface and a lateral surface, the light guide being configured to guide light entering from the end surface and emit linear light from the lateral surface; a light guide holder having a hole to receive the end surface of the light guide, and an opening optically communicating with the hole, the opening being formed in a first flat surface that is flat and opposite to a surface having the hole that receives the end surface of the light guide; a hole to receive the end surface of the light guide, and an opening optically communicating with the hole, the opening being formed in a first flat surface that is flat and opposite to a surface having the hole that receives the end surface of the light guide; a housing to house the light guide and the light guide holder and support the light guide holder with the end surface of the light guide exposed to an outside; the housing including a side wall, a light source base plate on which a light source element that emits light toward the end surface of the light guide is formed; and a base plate protection layer having a second flat surface that covers the light source base plate and is flat, the base plate protection layer being formed on a region of the light source base plate other than at least a region on which the light source element is formed, characterized in that: at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the housing with a bonding member therebetween or the at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the first flat surface of the light guide holder with the bonding member therebetween, at a position, in a direction along the longitudinal direction, at which the light emitted by the light source element enters the opening,and in a cross section intersecting with the longitudinal direction, the side wall is arranged between the light source base plate and the light guide holder in a region other than at least a portion at which the end surface of the light guide is exposed to the outside. at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the housing with a bonding member therebetween or the at least one of the light source base plate or the second flat surface of the base plate protection layer is pressed against the first flat surface of the light guide holder with the bonding member therebetween, at a position, in a direction along the longitudinal direction, at which the light emitted by the light source element enters the opening,and in a cross section intersecting with the longitudinal direction, the side wall is arranged between the light source base plate and the light guide holder in a region other than at least a portion at which the end surface of the light guide is exposed to the outside.