An image sensor unit includes a light condenser that collects light from a reading target object; an image sensor that receives light and converts the light into an electric signal; an elongated housing that houses the light condenser and the image sensor; and an elongated rigid member attached to a side surface extending in the elongated direction of the housing. The side surface of the housing is provided with an attachment protrusion. The rigid member is provided with an attachment hole that penetrates from a surface facing the side surface of the housing to a non-facing surface on the opposite side, and the non-facing surface of the rigid member is provided with a concave. The attachment protrusion is inserted into the attachment hole, and a part of the attachment protrusion is fit into the concave.