PURPOSE: To prevent the temperature of a sample from being rapidly lowered, by forming the wall of a bomb in a heat-insulating structure.

CONSTITUTION: A heat-insulating material 2 such as hollow-granule-like zirconia or the like is filled in a gap of double walls, that is, outer and inner walls 1a, 1b in the wall of a combustion bomb 1. With this arrangement, heat generated in the bomb 1 is transmitted, perpendicular to the wall of the bomb, so that the heat does not readily leaks outside. Further, the vertical distribution of the temperature inside of the inner wall 1b of the bomb 1 is made to be uniform so that the temperatures of gas and the sample in the bomb may be readily held. Further, heat from a small size heater 6 attached to the bottom a combustion pan 3 may prevent the temperature of the sample from being rapidly dropped due to the decay of flame heat during the end period of combustion of the sample 4.