A sample heating device includes: an opening/closing cover provided to be movable in a horizontal direction between a position above an opening of a mounting port and a position displaced from the position above the opening, and a cover sliding mechanism that is engaged with a part of a sample boat conveying portion when the sample boat conveying portion comes to a predetermined position in a horizontal plane and moves the opening/closing cover in the horizontal direction according to upward and downward movements of the sample boat conveying portion so that the opening/closing cover is provided at the position directly above the opening of the mounting port when the sample boat conveying portion comes to a predetermined height.