There is provided an optical storage apparatus which can properly form a tracking error signal (E2) even with respect to the presence or absence of a mirror portion due to a difference of a medium or a high speed seek. Therefore, the tracking error detection circuit (50) comprises a 2-split detector (46) for receiving the return light from said medium (72, 82) and converting into an electric signal (E5, E6); a subtracter (294) for forming the tracking error signal (E2) from a difference between photosensitive signals derived from said 2-split detector (46) and outputting; a peak holding circuit (290, 292) for detecting envelopes of the photosensitive signals from said 2-split detector (46) and outputting to said subtracter; and a switching control circuit (295) for on/off controlling an envelope detecting function by said peak holding circuit (290, 292) as necessary.