An image-forming device includes a first frame, and a first supporting unit. The first frame includes a first plate-shaped part having a surface orthogonal to the first direction and supports a first image-bearing member. The first plate-shaped part is formed with at least two first positioning holes. Each of the at least two first positioning holes is defined by a first inner surface that extends in the first direction. The first supporting unit erects from the first plate-shaped part and includes at least two first fitting parts and a first contact part. The at least two first fitting parts fit into the at least two first positioning holes. The first contact part extends in the first direction from each of the at least two first fitting parts. The first contact part contacts and supports the exposure unit. The exposure unit is oriented in a direction in which the light emitted from the plurality of light emitting elements is directed toward a second direction orthogonal to the first direction.