Automatic transmission

An automatic transmission, comprising:

• an input member disposed inside a casing and rotated by a driving force transmitted from a drive source;
• a planetary gear mechanism having a plurality of elements rotatable inside the casing;
• a plurality of engaging mechanisms switchable to a coupled state in which the elements are coupled to one another, or switchable to a fixed state in which the elements are fixed to the casing, comprising
• a switching mechanism switchable between the fixed state and a reverse rotation preventing state that allows a normal rotation and prevents a reverse rotation of corresponding elements among the plurality of elements;
• an output member outputting a rotation;
• and
• a control part controlling the engaging mechanisms and recognizing a rotational speed of the drive source and a stop request for the drive source, wherein
• the automatic transmission is configured to output a rotation of the input member to the output member while changing speed in a plurality of gear positions with the planetary gear mechanism and the engagement mechanisms, and
• the control part switches the switching mechanism in a state in which the stop request for the drive source is not recognized and the rotational speed of the drive source is equal to or greater than a predetermined value.