According to one embodiment, a signal processing circuit processes a signal read from a magnetic disk including a servo region and a user data region, the servo region including a servo address mark, the user data region including a data sector, and includes a counter and a gate controller. The counter is configured to count a first clock when having detected the servo address mark based on the signal read from the magnetic disk. The gate controller is configured to generate a pulse for locating the data sector in synchronization with a second clock when the counter counts a first value.