An image sensor module includes: a sensor IC having light receivers arranged in a main scanning direction; a lens unit configured to form an image on the sensor IC with light transferred from a read target; a first light source unit having a first output surface extending along the main scanning direction and outputting a first linear light extending along the main scanning direction from the first output surface toward the read target, the first output surface being placed at a position spaced apart from the lens unit in a sub-scanning direction; and a second light source unit having a second output surface extending along the main scanning direction and outputting a second linear light extending along the main scanning direction from the second output surface toward the read target, the second output surface being placed between the lens unit and the first output surface in the sub-scanning direction.