An automatic transmission device, comprising: a stepped transmission mechanism including a rotatable shift cam having a plurality of first engaging portions and a shift arm having a second engaging portion engageable with any of the first engaging portions; in which when the shift arm is moved from a neutral position to a gear position change position, the second engaging portion is put into engagement with one of the first engaging portions and the shift cam is rotated along with the movement of the shift arm, and thus change of gear position is performed; and when the shift arm is moved from the gear position change position to the neutral position, the second engaging portion is released from the engagement with the one of the first engaging portions and becomes engageable with another one of the first engaging portions; a shift actuator configured to give a driving force to the shift arm so as to move the shift arm from the neutral position toward the gear position change position, by moving from a start position to an end position, and configured to give the shift arm a driving force so as to move the shift arm from the gear position change position toward the neutral position, by moving from the end position to the start position; an urging member configured to urge the shift arm toward the neutral position; a gear change instruction output device configured to output a gear change instruction; and a shift actuator control device configured to control the shift actuator; characterized in that in the case where after a first gear change instruction is output from the gear change instruction output device, a second gear change instruction is output from the gear change instruction output device before the shift arm returns to the neutral position after moving from the neutral position to the gear position change position, the shift actuator control device is configured to control the shift actuator such that a driving force of the shift actuator becomes zero or smaller than an urging force of the urging member, after change of gear position based on the first gear change instruction is finished, and thus the shift arm is returned to the neutral position by the urging force of the urging member; and the shift actuator control device is configured to then control the shift actuator such that the shift arm is moved from the neutral position to the gear position change position, and thus change of gear position is performed based on the second gear change instruction. a stepped transmission mechanism including a rotatable shift cam having a plurality of first engaging portions and a shift arm having a second engaging portion engageable with any of the first engaging portions; in which when the shift arm is moved from a neutral position to a gear position change position, the second engaging portion is put into engagement with one of the first engaging portions and the shift cam is rotated along with the movement of the shift arm, and thus change of gear position is performed; and when the shift arm is moved from the gear position change position to the neutral position, the second engaging portion is released from the engagement with the one of the first engaging portions and becomes engageable with another one of the first engaging portions; a shift actuator configured to give a driving force to the shift arm so as to move the shift arm from the neutral position toward the gear position change position, by moving from a start position to an end position, and configured to give the shift arm a driving force so as to move the shift arm from the gear position change position toward the neutral position, by moving from the end position to the start position; an urging member configured to urge the shift arm toward the neutral position; a gear change instruction output device configured to output a gear change instruction; and a shift actuator control device configured to control the shift actuator; characterized in that in the case where after a first gear change instruction is output from the gear change instruction output device, a second gear change instruction is output from the gear change instruction output device before the shift arm returns to the neutral position after moving from the neutral position to the gear position change position, the shift actuator control device is configured to control the shift actuator such that a driving force of the shift actuator becomes zero or smaller than an urging force of the urging member, after change of gear position based on the first gear change instruction is finished, and thus the shift arm is returned to the neutral position by the urging force of the urging member; and the shift actuator control device is configured to then control the shift actuator such that the shift arm is moved from the neutral position to the gear position change position, and thus change of gear position is performed based on the second gear change instruction.