An image scanning device includes a linear light source to illuminate a linear illumination position of a scan target with light, a lens body, and a sensor. The linear light source includes a light guide, a scatterer, an emitter, a stepped portion, and a light-shielding member. The stepped portion is formed, from the end surface of the transparent body along the main scan direction, on a side of the light guide that is opposite to the illumination position side of the light guide. The light-shielding member covers a portion of the emitter of the light guide, the portion including the end surface of the transparent body, and extends beyond the stepped portion in the main scan direction and has an end portion that is located out of a scan range of the sensor in the main scan direction.