Embodiments of the present invention provide a write-current control chip capable of effectively preventing adjacent track interference (ATI) that occurs depending on how a magnetic disk drive is used, and to provide a magnetic disk drive using the write-current control chip. In one embodiment, a write-current control chip and a magnetic disk drive using the same are provided. The write-current control chip includes: an acquisition module for acquiring the number of times of write processing in which a magnetic head writes data to a magnetic disk in the magnetic disk drive; a determination module, on the basis of the acquired number of times of write processing, for determining a write-current value used when the magnetic head writes data to the magnetic disk; and an instruction mechanism for instructing the magnetic head to write the data to the magnetic disk by use of the determined write-current value.