A tracking error signal detection device employing a differential phase detection method includes first and second differentiators which remove direct current components in first and second signal groups in which a phase difference between the first and second signal groups changes in accordance with a tracking error signal, and which differentiate the first and second signal groups, first and second analog/digital converters which sample and quantize signals output from the first and second differentiators, respectively, a Hilbert transformer performing a 90-degree phase shift on one of signals output from the first and second analog/digital converters, a delay circuit delaying one of the signals output from the second and first analog/digital converters by an amount of delay equal to that caused by the Hilbert transformer, and a phase comparator calculating a phase difference between a signal output from the Hilbert transformer and a signal output from the delay circuit.