The invention provides a floppy disk apparatus which can perform, where a carriage motor which makes a non-linear operation such as a linear stepping motor is employed, suitable gain adjustment conforming to operation of a carriage. Upon setting of a correction gain, the position of a magnetic head on a floppy disk medium is fixed by a main control section, and in this condition, servo information is read out from the floppy disk medium. From the servo information read out by the magnetic head, a tracking error signal is produced by a tracking error production section. Based on the thus produced tracking error signal, an operation amount calculation section calculates an operation amount of the carriage for one rotation of the floppy disk medium. A correction gain setting section calculates a correction gain based on the operation amount calculated by the operation amount calculation section, and sets the thus calculated correction gain to an operation amount correction section.