To provide a sealing door for a pressure vessel, which has excellent durability of a fixed portion for a thin plate member and a projecting member when a sterilizing room 2 is depressurized by vacuuming.

In the sealing door 5 for the pressure vessel, a plurality of beam members 10 is adjacently juxtaposed in a direction crossing the thin plate member 9 on one side of the flexible thin plate member 9. The beam members 10 are fixedly attached to the thin plate member 9 not through an intermediate member. Thereby, when the thin plate member 9 receives a depressurization load, deformation of the thin plate member 9 caused across the fixed portion 20 for the thin plate member 9 and the beam members 10 is made symmetric, improving the durability of the fixed portion 20 for the thin plat member 9 and the beam members 10.