A thermal analyzer is provided with: a furnace tube; a pair of sample holders; a heating furnace; a measurement chamber; and a measurement unit arranged inside the measurement chamber. The sample holders are arranged inside the furnace tube and are provided with mounting faces on which a pair of sample containers are mounted respectively. The heating furnace has an opening through which a measurement sample is observable, the opening being located at a position above the center of a virtual segment which connects centers of gravity of the mounting faces of the sample holders. The opening is formed to have a size, as viewed in a direction perpendicular to the axial direction and the mounting faces, of 7 mm or more in the direction along the virtual segment and of 3 mm or more in the direction perpendicular to the virtual segment.
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