A magnetic disk drive, comprising: a slider, which is provided at a position facing to a disk surface; an arm, which is configured to conduct rocking motion around a pivot; a base, which is configured to support a motor thereon, which rotates the disk; a semiconductor laser module, which is configured to be fixed on the arm and stores a semiconductor laser element therein; a light irradiation portion upon the disk surface; and a wave guide, which is configured to build up an optical path between the light irradiation portion and the semiconductor laser module, wherein the semiconductor laser module and a portion of the base are connected therebetween by a flexible heat-conductive member having a predetermined curvature.