A diesel engine piston having a combustion chamber may include a profile surface that protrudes toward a center axis of the combustion chamber from an inner wall thereof and includes a protrusion on the inner wall, the protrusion extending from the inner wall with a predetermined length, wherein the protrusion divides a spray fuel, which may be sprayed and atomized onto the protrusion, into a fuel flow at an upper portion of the combustion chamber and a fuel flow at a lower portion of the combustion chamber, respectively.