An image forming apparatus for forming an image on a sheet, comprising: exposure devices configured to emit light to a charged image formation surface to form an electrostatic latent image; a support structure configured to support the exposure devices; and a housing configured to store the exposure devices, wherein the housing includes a first wall, which is provided with an insertion opening to insert the support structure that supports the exposure devices, and a second wall which faces the first wall, the support structure is designed so that the support structure is pulled out of the housing through the insertion opening, wherein the support structure includes a first frame plate, which extends in an insertion direction of the support structure, a second frame plate opposite to the first frame plate, and a third frame plate which is connected to the first and second frame plates (320, 330), characterized in that each of the first and second frame plates (320, 330) includes a first end (32R, 33R) at which a first positioning piece (321,331) is formed, the second wall includes an inner wall surface which is provided with a first positioning hole into which the first positioning piece (321, 331) is inserted, the support structure includes an attachment plate attached to the housing, a fourth frame plate situated between the attachment plate and the exposure devices, and a biasing element situated between the attachment plate and the fourth frame plate, the fourth frame plate opposite to the third frame plate is connected to the first and second frame plates (320, 330), and the biasing element biases the fourth frame plate toward the second wall. exposure devices configured to emit light to a charged image formation surface to form an electrostatic latent image; a support structure configured to support the exposure devices; and a housing configured to store the exposure devices, wherein the housing includes a first wall, which is provided with an insertion opening to insert the support structure that supports the exposure devices, and a second wall which faces the first wall, the support structure is designed so that the support structure is pulled out of the housing through the insertion opening, wherein the support structure includes a first frame plate, which extends in an insertion direction of the support structure, a second frame plate opposite to the first frame plate, and a third frame plate which is connected to the first and second frame plates (320, 330), characterized in that each of the first and second frame plates (320, 330) includes a first end (32R, 33R) at which a first positioning piece (321,331) is formed, the second wall includes an inner wall surface which is provided with a first positioning hole into which the first positioning piece (321, 331) is inserted, the support structure includes an attachment plate attached to the housing, a fourth frame plate situated between the attachment plate and the exposure devices, and a biasing element situated between the attachment plate and the fourth frame plate, the fourth frame plate opposite to the third frame plate is connected to the first and second frame plates (320, 330), and the biasing element biases the fourth frame plate toward the second wall.