An image forming device includes an inner guide, a first outer guide, a
second outer guide and a control device. A fusing casing is arranged
between the inner guide and a heat roller. The inner guide forms a
downstream end portion of a transportation path and a paper output path.
The first outer guide is arranged at a position facing an open portion of
a fusing casing across the transportation path, defines the downstream
end portion of the transportation path together with the inner guide, and
includes a hook-shaped portion curved to guide printing paper to the
paper output path. The second outer guide defines the paper output path
together with the inner guide, and defines an upstream end portion of the
reversal path. The control device controls a linear speed of a paper
output roller to be faster than a linear speed of a duplex transportation
roller at a switchback transportation of the printing paper.