A jacket of a steam sterilizer embedding a sterilization chamber (3) consisting of two separated and independent each other parts of which a heating part (1) of the jacket embeds the sterilization chamber (3) while a filling part (2) of the jacket is advantageously arranged in the bottom part of the sterilization chamber (3), said parts form the integral unit. Both the outlet of a first steam filling valve (4) and the inlet of a first pressure sensor (5) enter the heating part (1), and both the outlet of a steam filling valve (6) and the inlet of a second pressure sensor (7) and the inlet of a third steam filling valve (8) enter the sterilizing chamber (3) into which both the outlet of the third steam filling valve (8) and the inlet of a third pressure sensor (9) enter, enter the area of the filling part (2).