Servo data to be stored on a servo disk in a magnetic recording apparatus for positioning a data head of the magnetic recording apparatus to a data disk of the magnetic recording apparatus, are formed in a train of four servo bytes arranged in accordance with four clock bits successively received. Each servo byte consists of a clock bit and a group of positional bits respectively, where the positional bit is set making a definite time space from the clock bit. The four definite time spaces of the corresponding positional bit in the four servo bytes make an arithmetic progression, in which the initial term is the definite time space of the positional bit in the first servo byte and the common difference is the time difference between two corresponding positional bits in two adjacent servo bytes. The time difference and a length of a gate pulse in which servo data signals are demodulated, are set, for example, to 20 ns and 160 ns, respectively.