To provide an automatic transmission which reliably performs gear change by preventing that a shift arm and a protrusion part of a shift cam are not engaged with each other when performing the gear change continuously in a short time.

In an automatic transmission 40, when a second gear change instruction is outputted while a shift arm 425 returns from a gear step changing position to a neutral position after a first gear change instruction is outputted from a shift switch 8, the change of the gear step based on the first gear change instruction is ended, and thereafter, a shift actuator control part 140 controls a shift actuator 72 such that the driving force of the shift actuator 72 becomes zero or less than an energizing force of a spring 430. Thereby, the shift arm 425 is returned to the neutral position by the energizing force of the spring 430, and thereafter, the shift actuator 72 is controlled such that the shift arm 425 is moved from the neutral position to the gear step changing position, so that the gear step is changed based on the second gear change instruction.