An image reading device includes: a line illuminator for irradiating a document G; an erecting equal-magnification lens array operative to condense light reflected by the document G and including a stack of a first lens array plate and a second lens array plate each provided with an arrangement of a plurality of lenses on both sides thereof; a line image sensor operative to receive the light condensed by the erecting equal-magnification lens array; a housing for securing the line illuminator, the erecting equal-magnification lens array, and the line image sensor in their places; and a first light shielding member, a second light shielding member, and a third light shielding member operative to prevent light not contributing to imaging from entering the lenses. The first light shielding member, the second light shielding member, and the third light shielding member are formed as one piece with the main part of the housing.