A transfer unit includes a seamless transfer belt, a plurality of transfer rollers, a backup roller, a plurality of pairs of first bearing holders, a pair of second bearing holders and a pair of sliders. Each of the sliders is reciprocated such that each of the first bearing holders slides on the corresponding one of the first step ribs to be reciprocated in a direction toward and away from the transfer belt and the second bearing holder slides on the second step rib to be reciprocated in the direction toward and away from the transfer belt. The first step rib arranged most upstream in the direction of travel of the transfer belt and the second step rib are arranged side by side in the axial direction of the transfer roller, and overlap each other when viewed in the axial direction.