A pre-pit detecting apparatus detects a pre-pit with respect to an information record medium having a record track and a guide track which is to guide a light beam onto the record track and on which the pre-pit to record control information is formed in advance. The first pre-pit detecting apparatus is provided with: a light receiving device having four divided light detection areas each for receiving a reflection light of the light beam emitted on the record track. The four divided light detection areas are divided such that the reflection light beam is divided by a first division line which is optically in substantially parallel to the record track and a second division line which is optically in substantially orthogonal to the record track. The light receiving device outputs first to fourth light detection signals corresponding to the first to the fourth division areas respectively. The pre-pit detecting apparatus is also provided with: a first difference signal generation device for generating a first difference signal by subtracting the third light detection signal from the first light detection signal; a second difference signal generation device for generating a second difference signal by subtracting the second light detection signal from the fourth light detection signal; a correction device for delaying the second difference signal by a delay time; and a pre-pit detection signal output device for adding the first difference signal and the delayed second difference signal to output it as a pre-pit detection signal.