A medium conveyance route switching device includes a support unit, a gate assembly, and a rotation mechanism. The support unit is located at a branching point of a first conveyance path, a second conveyance path and a third conveyance path where conveyance directions of a medium converge in three directions. The gate assembly includes a first to a third gate positioned on one ends of the first to the third conveyance path to guide at the branching point the medium to other conveyance paths than a conveyance path from which the medium is conveyed. The rotation mechanism includes a first actuator rotating the first gate to switch the medium conveyed from the first conveyance path to the second conveyance path or the third conveyance path, and a second actuator, when the first gate is rotated, rotating the second gate and the third gate in associated with the second gate.