An optical recording and reproducing apparatus comprises an optical disc having a recording surface; a laser diode emitting a laser beam; an optical lens for changing the laser beam into a parallel laser beam; a diffraction grating for diffracting the parallel laser beam and generating 0-order and .+-.1st diffracted lights, a light intensity ratio of each of the .+-.1st diffracted lights to the 0-order diffracted light ranging from 8:1 to 9:1; and an optical system for forming spot lights of the 0-order and .+-.1st diffracted lights on the recording surface of the disc and extracting the 0-order and .+-.1st diffracted lights which have been reflected from on the recording surface.