A method, medium, and apparatus for performing path planning of a mobile robot is provided. The apparatus for performing path planning of a mobile robot includes a coarse map generation unit to generate a coarse map composed of a plurality of cells; a fine map generation unit to generate a fine map composed of a plurality of sub-cells into which at least one of the plurality of cells is divided, and a path generation unit to control the fine map generation unit to generate the fine map with respect to a specified position in the coarse map generated through the coarse map generation unit. The method of performing path planning of a mobile robot includes generating a coarse map composed of a plurality of cells, generating a fine map composed of a plurality of sub-cells into which at least one of the plurality of cells, which neighbors the cell where an obstacle exists, is divided, generating a moving path whereby the mobile robot can pass a narrow passage by using the fine map, and updating the coarse map by reflecting the moving path.