This paper presents an aerial robot with a manipulator to implement door opening mission. Although general aerial robots have advantages of flying in the three-dimensional space freely, they don't have any capability of moving to another room when the door is closed. To overcome this problem, we propose a new configuration of an aerial manipulator with perching function, knob-twisting function, and door-pushing function. Perching function can be achieved by integration of door-approach control, the mechanism for perching and attitude-change control. With regard to knob-twisting function, the design concept of a light-weight manipulator generating large enough force to twist the knob is introduced, which is composed of a soft-bag actuator with variable restriction to perform the arbitrary curved trajectory. On the other hand, the door pushing force is aimed to be generated by the lift of the propeller, which is helpful to avoid gaining the additional weight. The validity of the proposed methods is experimentally verified by using the developed prototype.