A disk storage device includes at least one disk, a head for scanning a principal surface of the disk in a generally radial direction thereof for reproducing a servo control signal in response to a servo pattern that is recorded on the principal surface, a rotary mechanism for moving the head along the principal surface of the disk generally in the radial direction, an amplifier supplied with the servo signal reproduced at the head for amplifying the same with a predetermined gain, a signal processing circuit for extracting first and second positional control signals each having a phase that is offset with respect to the phase of the other positional control signal by 90 degrees, from the servo control signal, a level detection circuit for detecting a head position at which the first and second positional control signals have simultaneously an identical level and further for detecting the level of the first and second positional control signals at the detected head position, a gain control circuit for controlling the gain of the amplifier such that an absolute value of the foregoing level is set to a predetermined value, and a head position control circuit for controlling a driving circuit in response to a combination of the first and second positional control signals, the head position control circuit locating the head on a predetermined recording track based upon a head position in which the first and second positional control signals have the same level simultaneously.