An image reading device is provided, which includes a controller configured to, when a carriage reaches a turn-around position in a moving direction, control a motor to once stop, then rotate in a second direction opposite to a first direction such that a planetary gear swings to a position separated from an output gear and that an intermediate gear moves to an engagement position to engage with the output gear, and thereafter again rotate in the first direction so as to transmit a driving force from the motor to the output gear via an input gear, a planetary gear, and the intermediate gear.