PURPOSE: To prevent the occurrence of an omission and a destruction of the data recorded in a data zone by stopping the rotation of a magnetic disk when CSS zone wear becomes excessive.

CONSTITUTION: Same initial data of a magnetic disk CSS zone and an initial data storage section are stored and when the magnetic disk device is activated, the initial data are read from the CSS zone by a magnetic head and the data are transmitted to a data comparison circuit. In this circuit, the data are compared with the initial data read from the initial data storage section and if these data are noncoincident, the rotation of the magnetic disk is stopped.