UAVs have been actively researched as a means of collecting information during disasters. In particular, helicopter-type UAVs using four rotors are often called an X4-Flyer, and it has been attracting attention. The X4-Flyer has excellent maneuverability, compared to conventional helicopters that change the angle of attack of the rotor. Therefore it can be used at a space such as indoor or low altitude in which many obstacles exist. When the X4-Flyer is used at such a space, it needs to fly not so as to collide with obstacles, and so the precise control of the X4-Flyer is required. The objective of this research is to develop the X4-Flyer that can fly while detecting and avoiding obstacles. This paper presents the attitude and altitude stabilization of the X4-Flyer. We describe on measuring of the physical parameters related to the rotors and on correcting individual differences in motors, and finally conduct a hovering experiment.