This paper proposes on-demand type feedback controller for state space based generalized minimum variance control (GMVC) using coprime factorization. GMVC can be extended by using coprime factorization, and a new design parameter is introduced to the extended controller. Then the parameter can determine the characteristics of the extended controller without changing the closed-loop characteristics. In order to design safe systems, strong stability systems are effective because both closed-loop system and the controller are stable. So the parameter mentioned above is seemed to be useful to design safe systems. Moreover, focusing on feedback signal, the extended controller can adjust the magnitude of the feedback signal. It means that the proposed controller has the possibility to make the magnitude of the feedback signal be zero when the control objective is achieved. In other words the proposed method has the ability that the feedback signal emerges on demand of achieving the control objective. Therefore this paper explores the design method of on-demand type feedback controller using state space based GMVC and coprime factorization. A numerical example is given in order to check the characteristics of the proposed method.