A disk storage apparatus including a position detection section for producing position error information corresponding to the current position of a head from servo information which has been previously recorded on a disk and is detected by the head, a position control section for producing position control information corresponding to the position error information, a voltage detection section for detecting a voltage generated in driving an actuator for positioning the head with respect to the disk, and for outputting a voltage signal, a disturbance estimation section for estimating the magnitude of a disturbance exerted on the head from the voltage signal by the voltage detection section and from a drive signal by a drive section of the actuator, and producing disturbance estimation information, a correction section for correcting the position control information by the position control section with the disturbance estimation information and producing the drive signal, and a disturbance monitor section for monitoring the disturbance estimation information, and prohibiting a record by the head if the disturbance estimation information exceeds an allowable range, wherein even if the head is largely dislocated from a target track due to a large shock or vibration at data recording, an erroneous erasing of the adjacent track can be prohibited.