An optical head, an optical disc device and an information processing device are capable of suppressing the amount of third-order astigmatism created upon recording or reproducing information on or from a multi-layer optical disc including at least three information recording surfaces. An objective lens satisfies a relationship of tc>(t0+tn)/2 assuming that t0 denotes the thickness of a light transmitting layer from the outer surface of the multi-layer optical disc to an information recording surface having the largest light transmitting layer thickness, tn denotes the thickness of a light transmitting layer from the outer surface of the multi-layer optical disc to an information recording surface having the smallest light transmitting layer thickness and tc denotes the thickness of a virtual light transmitting layer at which the absolute value of a third-order spherical aberration is minimum when blue-violet laser light is incident as parallel light on the objective lens.