The invention relates to an illuminating apparatus, an image reading apparatus and an image forming apparatus. In an illuminating apparatus including a plurality of rows of light source groups each having a plurality of light-emitting elements for irradiating light to an original that are arranged in a main scanning direction, the light-emitting elements in the plurality of rows of light source groups illuminate an irradiated face of the original at the same pitch within the same light source group and at different pitches from each other among the plurality of rows of light source groups.