Various embodiments of a lip moving device for use in robots are provided. A lip moving device has first and second lip members. The first and second lip members are made from a flexible material. First and second driving parts apply torques to both ends of the first lip member, while third and fourth driving parts apply torques to both ends of the second lip member. The first and third driving parts are mounted in a first frame. The second and fourth driving parts are mounted in a second frame. The first and second frames are pivotally coupled to a supporting part. An adjusting part pivots the first and second frames relative to the supporting part to adjust a distance between the first and second frames.