1. A simultaneous localization and mapping (SLAM) apparatus of a robot, comprising: a converter to convert a two-dimensional (2D) position of measured feature data in a first coordinate system to a three-dimensional (3D) position in a second coordinate system based on a preset depth of the measured feature data, the depth of the measured feature data having been preset to a predetermined value; and an updater to update pre-existing registered feature data in a third coordinate system and corresponding to the measured feature data, by converting the registered feature data from the third coordinate system to the second coordinate system and comparing, in the second coordinate system, the converted 3D position of the measured feature data with a corresponding 3D position of the converted registered feature data.