A combustion chamber of a direct-injection Diesel engine in which a throttle (73) is provided at the inlet of a combustion chamber (72), a plurality of recesses (74) are formed in the side surface of the chamber (72), and fuel nozzles (75) having one more jet ports than the number of the recesses (74) are provided at equal intervals for injecting fuel. When the recesses (74) are formed, the thickness of the top face (78) of the piston is reduced, and thermal breakage can occur at steps in valve escapes (79, 80) if the valve escapes (79, 80) of gas supply and exhaust valves are recessed into the piston (71). Accordingly, steps (81, 82) for the escapes (79, 80) are formed in the recesses (74). Further, the side surface (77) of the combustion chamber onto which sprayed fuel hits is inclined so that it is at an angle of 45o to the top surface (78) of the piston. With the above structure, the optimal combustion can be obtained over the entire rotational zone, and steady combustion can also be obtained.