An objective of the present disclosure is to obtain a light guide and an image reading apparatus capable of efficiently irradiating an object to be irradiated (1). The light guide and the image reading apparatus include a rod-shaped light guide main body (2) extending in the longitudinal direction, a first end face (3) that is an end face of the light guide main body (2) along the transverse direction, a light scattering pattern (5) that scatters light that enters from the first end face (3) and is guided inside the light guide main body (2), and a light emission surface portion (6) formed on the light guide main body along a longitudinal direction, the light emission surface portion (6) being a surface from which the light scattered at the light scattering pattern (5) is emitted to outside the light guide main body (2) after being reflected on a wall surface of the light guide main body (2).The light emission surface portion (6) includes a first light emission surface (6a) that is disposed near the first end face (3) in the longitudinal direction and a second light emission surface (6b) that is contiguous with the first light emission surface (6a) in the longitudinal direction. A width of the first light emission surface (6a) in the transverse direction is shorter than a width of the second light emission surface (6b) in the transverse direction.