CONTROLLER AND CONTROL METHOD

The invention obtains a controller and a control method capable of appropriately assisting with an operation by a driver while preventing a motorcycle from falling over. In the controller and the control method according to the invention, in a control mode to make the motorcycle perform an automatic cruise deceleration operation, automatic deceleration that is deceleration of the motorcycle generated by the automatic cruise deceleration operation is controlled in accordance with a change rate of a state amount that is related to posture of the motorcycle during turning travel.