An optical information recording and reproducing apparatus for an optical information record medium on which a plurality of tracks are arranged substantially in parallel, comprises a light source, a first optical system for guiding a light beam from the light source, onto the record medium, a second optical system for obtaining the light beam from the record medium, a detecting device for receiving the light beam obtained by the second optical system to output at least one of a focusing signal and a tracking signal, an adjusting device for adjusting at least one of focusing and tracking operation in accordance with at least one of the focusing and tracking signals, a reciprocating device for causing the record medium to reciprocate, a control device for controlling the reciprocating device, and a change device for changing at least a servo gain of the adjusting device in accordance with at least a signal from the control device.