PROBLEM TO BE SOLVED: To enable evaluation of the quality and the characteristics of a plant cultivation container, made of nonwoven fabric or woven fabric by penetrating a raw material to be measured to the constant position at a constant speed from the tip by a conical jig, wherein the surface is processed to a specified roughness and the specified tip angle is provided. SOLUTION: A conical jig made of stainless steel, wherein the surface roughness is processed to 0.8μm or less and the tip angle of a conical part 3 is adjusted to about 20 degrees, is attached to an attaching part 5 of a tensile tester by an attaching part 4. In the meantime, a raw material to be measured 6 such as plant cultivation container made of nonwoven fabric or woven fabric is bridged between an upper fixing ring 7 and a lower fixing ring 8 of a burst-strength measuring instrument, provided at a position facing the jig and fixed with a screw 9. Then, the conical part 3 is penetrated at a penetration speed in the range of 5-20mm/minute from the vertical direction with respect to the raw material to be measured 6. The load at this time, that is to say, the resistance value is measured. Thus, the quality of the performance and the characteristics of the raw material can be judged, and the results can be utilized for correcting the constitution of the raw material.
