To effectively attenuate the noise of steam injected from a cooker by attaching a noise reducing structure to the inner part of a cylinder part and at least stopping-off the right upward ascent of steam which is injected from the vapor port of the cooker.

Steam S injected from the vapor port 20 of the cooker 10 comes from the opening part 100 into a base part 1 and expands in a circumferential space (a) enclosed by the base part 1 so that the noise of steam S is attenuated by means of first order. Then expanded and diffused steam S is made to easily flow into the narrow ventilation square hole 14 of the base part 1, steam S made to flow into the hole 14 of the base part 1 is compressed in a gap (b) between the main body 21 of the cylinder part 2 and a noise reducing boards 3 and expanded between the upper and lower noise reducing boards 3 so that noise is secondarily attenuated. Then the noise of steam S injected from the vapor port 20 of the cooker 10 is surely attenuated in result. A noise absorbing material 5 is laminated on a surface to which steam S coming from the port 20 of the cooker 10 is injected, the noise of the steam S is directly absorbed and attenuated and, then, the occurrence of the collision noise of steam S on respective surfaces is prevented.