An image reading apparatus comprising: a plurality of point light sources, arranged in a straight line state, configured to output light for lighting a document situated on a contact glass from a lower side of the contact glass; a light leading member, positioned in front in a light outputting direction of the light output from the point light sources, configured to lead the light output from the point light sources so as to irradiate along a main scanning direction toward the document situated on the contact glass; and a photoelectric conversion element (16, 17) configured to receive reflection light from the document; wherein the light leading member includes positioning means configured to make a gap between each of the point light sources arranged in a line state and the light leading member constant and make an arrangement direction of the point light sources be positioned along a longitudinal direction of the light leading member; characterized by, further comprising: a point light source array substrate where the point light sources are provided in the line state; wherein the positioning means is formed by a holding part and a contact standard surface; the holding part is provided in the light leading member; the holding part has a mounting surface extending in parallel with the longitudinal direction of the light leading member, the mounting surface being where the point light source array substrate is mounted; and the contact standard surface is formed in the light leading member and has a structure where a contact surface formed in the substrate contacts the contact standard surface by mounting the point light source array substrate on the mounting surface. a plurality of point light sources, arranged in a straight line state, configured to output light for lighting a document situated on a contact glass from a lower side of the contact glass; a light leading member, positioned in front in a light outputting direction of the light output from the point light sources, configured to lead the light output from the point light sources so as to irradiate along a main scanning direction toward the document situated on the contact glass; and a photoelectric conversion element (16, 17) configured to receive reflection light from the document; wherein the light leading member includes positioning means configured to make a gap between each of the point light sources arranged in a line state and the light leading member constant and make an arrangement direction of the point light sources be positioned along a longitudinal direction of the light leading member; characterized by, further comprising: a point light source array substrate where the point light sources are provided in the line state; wherein the positioning means is formed by a holding part and a contact standard surface; the holding part is provided in the light leading member; the holding part has a mounting surface extending in parallel with the longitudinal direction of the light leading member, the mounting surface being where the point light source array substrate is mounted; and the contact standard surface is formed in the light leading member and has a structure where a contact surface formed in the substrate contacts the contact standard surface by mounting the point light source array substrate on the mounting surface. a point light source array substrate where the point light sources are provided in the line state; wherein the positioning means is formed by a holding part and a contact standard surface; the holding part is provided in the light leading member; the holding part has a mounting surface extending in parallel with the longitudinal direction of the light leading member, the mounting surface being where the point light source array substrate is mounted; and the contact standard surface is formed in the light leading member and has a structure where a contact surface formed in the substrate contacts the contact standard surface by mounting the point light source array substrate on the mounting surface.