Isostatic breaking strength tester and isostatic breaking strength test method

A breaking strength tester includes: a tubular pressure container having opened both ends to house a part of a pillar-shaped honeycomb structure including a partition walls and a circumferential wall; a tubular pressurization elastic body disposed to surround an entire circumference of a pressurized portion having a length equal to or less than ½ of a length in an axial direction of the circumferential wall; a partial pressurization unit which elastically deforms the pressurization elastic body and applies uniform pressure to the entire circumference of the circumferential wall of the pressurized portion of the honeycomb structure housed in the pressure container up to pressure test strength; and a pressure measurement unit which measures a value of the uniform pressure applied to the circumferential wall by the pressurization elastic body.