Abstract: The present invention provides a heat treatment apparatus which can increase in size without leading to a decrease in heat transfer performance. The heat treatment apparatus performs heat treatment of treatment objects inside a cylindrical body by heating the cylindrical body rotating around an axis, and the heat treatment apparatus includes a pair of movable support parts provided on both ends side along the axis of the cylindrical body so as to be able to move along the axis and rotatably supporting the cylindrical body around the axis, and a fixed support part provided between the pair of the movable support parts along the axis so as to be unable to move along the axis and rotatably supporting the cylindrical body around the axis, wherein the cylindrical body is supported by a three-point support of the pair of the movable support parts and the fixed support part.