To provide an image sensor unit obtaining uniform illumination distribution by preventing leakage light without using an additional component such as a conductor cover and to provide an image reader.

An image sensor unit 4 includes: a sensor substrate 14 where a plurality of photoelectric converters 13 are mounted; an original illumination light source 10 having a light emitting element; a conductor 11 which leads light from the light source 10 from one end face in a longitudinal direction and illuminates the original in a line shape; a rod lens array 12 which image-forms reflection light from the original on the sensor substrate 14; and a frame 15 to which they are attached. The frame 15 detachably includes a first spacer 16a arranged near the light source 10 and a second spacer 16b arranged near the other end face in the longitudinal direction of the conductor 11. The first spacer 16a includes the light source 10 and a shading roof 20 extended to cover an end of the conductor 11.