The objective of the present invention is to provide: a robot arm extension device capable of adjusting an operating radius according to the operation environment and requirements of a robot in industrial sites; and a robot including the robot arm extension device. The robot arm extension device according to the present invention comprises: a housing; an adapter formed on one side of the housing and connected to the robot; a length extending part embedded in the housing and withdrawn from or inserted into the housing; and a driving part for providing the driving power of the length extending part.