A combustion chamber structure for a direct injection diesel engine is provided which can increase recirculated amount of exhaust gas while avoiding generation of black smoke and deterioration of fuel efficiency as much as possible.Disclosed is a combustion chamber structure for a direct injection diesel engine having a cavity 10 on a top surface of a piston 9. The cavity is concave to provide a majority of the combustion chamber. Fuel is injected from a center of a cylinder top radially into an inner periphery of the cavity 10 to self-ignite. A depression 24 is formed at an outer periphery of the cavity 10 and is sunken relative to the top surface of the piston 9 to provide a step. The depression 24 has a bottom with an outer periphery gradually rising radially outwardly in modestly curved surface to the top surface of the piston 9. The inlet lip 11 is formed at a position lower than the top surface of the piston 9 by an inner periphery of the bottom of the depression 24 and a combustion chamber wall 12 rising from a bottom of the cavity 10.