An image forming apparatus includes an image bearer; a toner image forming unit, a transfer unit, a detector, and a controller. The toner image forming unit forms a plurality of types of density detection patterns on the surface of the image bearer in mutually-different positions in a surface-movement direction of the image bearer. The density detection patterns have mutually-different lengths in a direction orthogonal to the surface-movement direction of the image bearer. The transfer unit transfers the density detection patterns onto the surface of the transfer member. The detector detects image densities of the density detection patterns transferred on the surface of the transfer member. The controller calculates an image density difference between the density detection patterns on a basis of a detection result obtained by the detector, and corrects a transfer bias for transferring a toner image on a basis of a value of the image density difference.