PURPOSE: To exactly execute a tracking servo by generating a tracking error signal, based on the ratio of levels of pilot signals leaking from a second and third tracks being adjacent to a first track.

CONSTITUTION: With respect to tracks T12, T13 traced by heads 12, 13, levels of pilot signals P leaking from the tracks T12, T13 being adjacent to one side are latched to a latching circuit 32. Also, with respect to the tracks T12, T13 traced by the heads 12, 13, the levels of pilot signals P leaking from the tracks T12, T13 being adjacent to the other side are latched to a latching circuit 33. Subsequently, these level detecting signals are supplied as addresses to a read only memory (ROM) 34. This ROM 34 derives the ratio of outputs of both the latching circuits 32, 33, transforms its ratio to, for instance, a logarithm and generates a tracking error signal. Thereafter, the tracking error signal is supplied to a latching circuit 35, in which a tracking error signal is generated.