An automatic transmission apparatus for a straddle-type vehicle having an engine, a driving wheel, and a power transmission mechanism configured to transmit mechanical power of the engine to the driving wheel, the automatic transmission apparatus comprising: an electric throttle valve provided in an air-intake passage of the engine; a clutch, provided in the power transmission mechanism, and configured to transmit and to interrupt the mechanical power of the engine; a clutch actuator configured to drive the clutch; a multi-geared type transmission mechanism, disposed between the clutch in the power transmission mechanism and the driving wheel, and having a dog clutch; a shift actuator configured to drive the transmission mechanism; and a control device configured to control the electric throttle valve so as to increase or decrease an opening of the electric throttle valve in gear-shifting, and to control the clutch actuator and the shift actuator so as to cause disengagement of the clutch, changing of a gear position of the transmission mechanism, and engagement of the clutch, the control device comprising: a clutch signal supplying unit configured to supply an actuation signal to the clutch actuator; a clutch position detecting unit configured to detect a position of the clutch; a shift signal supplying unit configured to supply an actuation signal to the shift actuator at or after a time at which a predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal; a determining unit configured to acquire, from the clutch position detecting unit, a position of the clutch at the time at which the predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal, and to determine whether or not the position of the clutch is equal to or less than a threshold value; and a shift signal prohibiting unit configured to prohibit the shift signal supplying unit from supplying the actuation signal if the determining unit determines that the position of the clutch is equal to or less than the threshold value at the time the predetermined time has elapsed. an electric throttle valve provided in an air-intake passage of the engine; a clutch, provided in the power transmission mechanism, and configured to transmit and to interrupt the mechanical power of the engine; a clutch actuator configured to drive the clutch; a multi-geared type transmission mechanism, disposed between the clutch in the power transmission mechanism and the driving wheel, and having a dog clutch; a shift actuator configured to drive the transmission mechanism; and a control device configured to control the electric throttle valve so as to increase or decrease an opening of the electric throttle valve in gear-shifting, and to control the clutch actuator and the shift actuator so as to cause disengagement of the clutch, changing of a gear position of the transmission mechanism, and engagement of the clutch, the control device comprising: a clutch signal supplying unit configured to supply an actuation signal to the clutch actuator; a clutch position detecting unit configured to detect a position of the clutch; a shift signal supplying unit configured to supply an actuation signal to the shift actuator at or after a time at which a predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal; a determining unit configured to acquire, from the clutch position detecting unit, a position of the clutch at the time at which the predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal, and to determine whether or not the position of the clutch is equal to or less than a threshold value; and a shift signal prohibiting unit configured to prohibit the shift signal supplying unit from supplying the actuation signal if the determining unit determines that the position of the clutch is equal to or less than the threshold value at the time the predetermined time has elapsed. a clutch signal supplying unit configured to supply an actuation signal to the clutch actuator; a clutch position detecting unit configured to detect a position of the clutch; a shift signal supplying unit configured to supply an actuation signal to the shift actuator at or after a time at which a predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal; a determining unit configured to acquire, from the clutch position detecting unit, a position of the clutch at the time at which the predetermined time has elapsed since the clutch signal supplying unit has supplied the actuation signal, and to determine whether or not the position of the clutch is equal to or less than a threshold value; and a shift signal prohibiting unit configured to prohibit the shift signal supplying unit from supplying the actuation signal if the determining unit determines that the position of the clutch is equal to or less than the threshold value at the time the predetermined time has elapsed.