Disclosed is a lubrication structure for an engine comprising pistons 12 for slide motion in cylinders 11 of a V-type engine and lubricating means 13 and 14 for injection of oil to cool the pistons 12. The lubricating means 13 or 14 being arranged on an anti-thrust load side of each of the cylinders 11 with respect to a sliding surface for the piston 12, a notch of each of the pistons 12 required for said lubricating means 13 and 14 being formed on the anti-thrust load side of the cylinder 11 so as to increase strength of the cylinders 11 and pistons 12.