An opening/closing device for openably/closably supports an opening/closing part with regard to an opened/closed part, and the opening/closing device is characterized in that it comprises an attaching part attached to the opened/closed part so as to rotate around a rotation axis together with the opening/closing part, a rotation part rotatably attached to an attaching portion extending from a rotation center of the attaching part and engaged with the opened/closed part, and a friction torque generation means provided between the attaching portion of the attaching part and the rotation part, as well as in that the opening/closing device is so configured that it can bring the opening/closing part to stop using free-stop function, when the opening/closing part is opened and closed with regard to the opened/closed part.