<p>A portable-type disk apparatus for a 3.5-inch or less optical disk implemented in a thin, light-weight and miniaturized structure having a vibration-withstanding capability. An optical head assembly is disposed stationarily while an optical disk (5) and a spindle motor (6) for rotating the optical disk (5) are disposed movably in a diametrical direction of the optical disk. The spindle motor (6) is constituted by a brushless motor of a substantially semi-circular form in cross section and having a laterally truncated portion. The optical head assembly including an optical head and a laser circuit is disposed at the side of the laterally truncated portion. <IMAGE></p>
