According to one embodiment, a magnetic disk device includes a disk having first servo data including a first preamble, a first servo mark, a first gray code, first burst data, and second burst data written after the first burst data, a head including a write head that writes data to the disk and a first read head and a second read head that read data from the disk, and a controller that reads the second burst data using the first read head and the second read head and calculates a servo demodulation position when the first servo data is servo-read without reading the first burst data in a short servo mode in which the first preamble, the first servo mark, and the first gray code are not read.