An X ray diffraction study on w¿stite (Fe0.98O) was performed up to 120 GPa at room temperature and up to 160 ¿C at 24 GPa using a diamond-anvil-type, high-pressure apparatus. W¿stite transforms from the cubic rock salt structure into a distorted structure with a rhombohedral unit cell at about 16 GPa at room temperature, and retrogressive transition occurs when the distorted phase is heated to 160 ¿C at 24 GPa. This transition can be explained as the paramagnetic to antiferromagnetic transition resulting from the increase of the N¿el temperature of w¿stite under high pressure. No further discontinuous change in the X ray diffraction pattern was observed up to 120 GPa at room temperature. This result is in disagreement with shock compression experiments, which have indicated the existence of a large discontinuous volume decrease at approximately 70 GPa.