A multistage steaming machine comprising: i) a steam chamber main body portion including two side portions facing each other in a first direction, one of the two side portions being a side portion of an inlet side through which a group of noodle strings is introduced, the other of the two side portions being a side portion of an outlet side through which the group of noodle strings is discharged; ii) a tunnel-type noodle introducing portion connected to an upper portion of the inlet side of the steam chamber main body portion and provided such that the group of noodle strings is carried in to the steam chamber main body portion in an obliquely upward direction; iii) a tunnel-type noodle discharging portion connected to the outlet side of the steam chamber main body portion and provided such that the group of steam-boiled noodle strings is carried out from the steam chamber main body portion in an obliquely downward direction; iv) a first conveyor configured to convey the group of noodle strings from the inlet end of the noodle introducing portion to the steam chamber main body portion and further convey the group of noodle strings in the forward direction to the noodle discharging portion; and a second conveyor configured to receive the group of noodle strings, which has been conveyed in the forward direction in the steam chamber main body portion, from the first conveyor, convey the group of noodle strings in the opposite direction to the inlet side of the steam chamber main body portion, and transfer the noodle strings to the first conveyor again such that the group of noodle strings which has been introduced from the noodle introducing portion through the upper portion of the steam chamber main body portion into the steam chamber main body portion goes and returns plural times along the first direction in the steam chamber main body portion to be conveyed to a lower side of the steam chamber main body portion and is then discharged through the noodle discharging portion, wherein an uppermost stage portion of the first conveyor forms a first region; and v) one or a plurality of steam pipes configured to supply steam to the steam chamber main body portion, wherein an inlet end of the noodle introducing portion and an outlet end of the noodle discharging portion are located lower than a lower end surface of the steam chamber main body portion; characterised in that said one or a plurality of steam pipes are provided at an upper portion side in the steam chamber main body portion only under the first region; and in that a member that is a plate-shaped body is inserted so as to fill an internal space of the second conveyor. i) a steam chamber main body portion including two side portions facing each other in a first direction, one of the two side portions being a side portion of an inlet side through which a group of noodle strings is introduced, the other of the two side portions being a side portion of an outlet side through which the group of noodle strings is discharged; ii) a tunnel-type noodle introducing portion connected to an upper portion of the inlet side of the steam chamber main body portion and provided such that the group of noodle strings is carried in to the steam chamber main body portion in an obliquely upward direction; iii) a tunnel-type noodle discharging portion connected to the outlet side of the steam chamber main body portion and provided such that the group of steam-boiled noodle strings is carried out from the steam chamber main body portion in an obliquely downward direction; iv) a first conveyor configured to convey the group of noodle strings from the inlet end of the noodle introducing portion to the steam chamber main body portion and further convey the group of noodle strings in the forward direction to the noodle discharging portion; and a second conveyor configured to receive the group of noodle strings, which has been conveyed in the forward direction in the steam chamber main body portion, from the first conveyor, convey the group of noodle strings in the opposite direction to the inlet side of the steam chamber main body portion, and transfer the noodle strings to the first conveyor again such that the group of noodle strings which has been introduced from the noodle introducing portion through the upper portion of the steam chamber main body portion into the steam chamber main body portion goes and returns plural times along the first direction in the steam chamber main body portion to be conveyed to a lower side of the steam chamber main body portion and is then discharged through the noodle discharging portion, wherein an uppermost stage portion of the first conveyor forms a first region; and v) one or a plurality of steam pipes configured to supply steam to the steam chamber main body portion, wherein