Using Atacama Large Millimeter/submillimeter Array (ALMA), we have resolved both molecular line and dust continuum emission around a forming O-type protostar, IRAS 18089-1732, with sub-arcsecond (<0.4′′) angular resolutions to test its accretion disk scenario previously suggested in the innermost ~3600 AU region of its circumstellar environment. Our 1.33mm continuum observations in Config. 5 and 8 show a compact component associated with extended arm-like structures at 0.05′′ resolution. The molecular line observations further resolve the kinematics in the central region and clearly show a rotating kinematics. Multiple <i>K</i> components of the <i>J</i>=12?11 transitions of CH<sub>3</sub>CN show a consistent rotation pattern resembling an accretion disk around the protostar.