Abstract: A circulatory steam sterilizer and, in particular, the circulatory steam sterilizer having a steam boiler poised in a transverse array and its two ends respectively joined with two-tier compartment partition plates which are arranged in an asymmetrical manner in a plurality of layers and the inner compartment partition plates are connected and in communication with the transversely arranged conduits. The conduits in the upper-most conduits for discharge and delivery are connected and communicative to the outer compartment partition plates, and then these inner conduits are transversely arranged in the inner part of the conduits in the lower layer to specially generate the inner and outer double circulatory heating, thereby achieving the multi-purpose practical benefits live circulatory preheating, heated sterilization and cooling as its features.