PROBLEM TO BE SOLVED: To provide a tracking error signal detecting device that the problem of an offset due to differences among gain characteristics and/or pit depths is solved by improving the split structure of an octapertite photodetector, and to provide a reproduced signal detecting device that crosstalk noise is reduced. SOLUTION: This tracking error signal detecting device is provided with a photodetector and a circuit part. It is characterized by that the photodetector is provided with four light receiving areas whose split boundary lines are parallel with lines corresponding to the radius direction and the tangential direction of a recording medium respectively and which are arranged in a counter-clockwise direction and the four light receiving areas are bisected so as to have inside slit plates and outside split plates whose widths following to the radius direction are changed at positions of ± tangential directions from center parts of respective photodetectors to form eight of inside and outside split plates forming a matrix with 2 rows and 4 columns and the circuit part is provided so as to detect a tracking error signal from phase difference signals after comparing phases between inside and/or outside split plates positioned at the same rows with each other.
TRACKING ERROR SIGNAL DETECTING DEVICE AND REPRODUCED SIGNAL DETECTING DEVICE