The invention obtains a controller and a control method capable of improving drivability of a motorcycle. In the controller and the control method according to the invention, an execution section of the controller executes positional relationship adjustment operation to control a positional relationship between a motorcycle and a preceding vehicle to a target positional relationship by automatically generating acceleration or deceleration to the motorcycle. During execution of the positional relationship adjustment operation, the execution section executes: first control operation for enabling and suspending execution of positional relationship approaching operation in which the positional relationship between the motorcycle and the preceding vehicle is controlled to be closer than the target positional relationship; and second control operation for executing the positional relationship approaching operation when determining that a rider of the motorcycle has an intention to overtake the preceding vehicle while the positional relationship approaching operation is suspended. During the execution of the positional relationship adjustment operation, the execution section executes notification operation for notifying the rider of information on the positional relationship approaching operation.
