The investigations of metasurfaces have introduced a new direction in researching metamaterials. We propose an ultrathin acoustic metasurface consisting of a series of structurally simple microunits. The microunit is constructed with a cavity filled with air and a membrane to seal the air. The designed metasurfaces can arbitrarily manipulate the reflected sound waves at 3.7 kHz. We also realize the planar focusing effects by elaborately arranging the microunits on the metasurfaces, including an axicon and a lens. The designed metamaterials may promote the development of many acoustic devices, such as cloaking, absorber, and spectrum splitter.