A fall detection device that is allowed to reduce the processing load put when making a determination using software, to reliably determine the start of a fall, and to make a fall prediction as necessary, and a magnetic disk drive and a portable electronic apparatus that each include the fall detection device are configured. Accelerations are obtained in three orthogonal axis directions (ax, ay, az), and an evaluation value is obtained with respect to each of the accelerations (ax, ay, az) on the basis of an evaluation function, by which an evaluation value is increased as the difference increases between accelerations (ax0, ay0, az0) at a steady time and accelerations (ax, ay, az) at a fall determination time, and whether a fall has started is determined on the basis of whether this evaluation value exceeds a predetermined value.
