The invention provides a combustion chamber of a direct injection diesel engine for reducing the nox. Disclosed is a combustion chamber of a diesel engine provided with a bowl having a concave shape so that fuel injected from an injector creates a swirl or squishing flow to be mixed with air, and the combustion chamber of the diesel engine includes: a pip protruding from a center of a lower surface of the bowl toward the injector; a lip part protruding from a side surface of the bowl toward the injector; and a main combustion chamber provided on a lower portion of the lip part and a sub combustion chamber provided on an upper portion of the lip part, with the lip part interposed therebetween, in which a surface of the sub combustion chamber is formed in a flat shape or a concave bowl shape to have a depth of the sub combustion chamber of 0.8 mm or lower.