PROBLEM TO BE SOLVED: To provide a steam circulation-type autoclaving sterilizer for sterilizing a treatment target by blowing steam thereto.SOLUTION: This device is a pressure vessel of a dual structure having a jacket 10 around a heating chamber 1 a steam circulation pipe (5b) into which steam streams and a steam circulation pipe (5a) out of which steam streams are connected to the heating chamber 1, and steam is circulated by configuring, at a midpoint of the steam circulation pipes, a fan chamber 2 having a fan 3 rotated by a motor 4, whereas a treatment target configured within the heating chamber is sterilized by blowing steam thereto.
