A blast treatment method for blasting an object includes: a step in which an explosive is detonated inside a pressure vessel (30) which has an elasto-plastic metal, thereby imparting to the pressure vessel (30) an initial load wherein the primary and secondary stress generated in at least a portion of the pressure vessel becomes high enough to be in a plastic region exceeding the elastic region, thereby generating a shakedown state in the pressure vessel (30); and a subsequent step in which a treatment explosive (50) is detonated within the pressure vessel (30), thereby blasting the object (10).