The invention intends to provide an atomic absorption spectrophotometer which can establish a uniform heat distribution during heating of a sample and can improve analysis accuracy and analyzing efficiency. For this purpose, a graphite tube type cuvette mounted in a graphite atomizer furnace for an atomic absorption spectrophotometer comprises a large-diameter portion for retaining a sample in place, a small-diameter portion connected to the large-diameter portion and having a smaller diameter than the large-diameter portion, and a step portion for demarcating between the large-diameter portion and the small-diameter portion. The graphite tube type cuvette is formed such that its cross-sectional area in a plane perpendicular to the direction of passage of an electric current supplied to the cuvette is the same in any of the large-diameter portion, the small-diameter portion and the step portion. The amount of resistance heat is thereby also the same in any portions.