A shelf assembly for firing including plural struts for supporting shelf boards arranged upright in two or more rows in a cross direction and in three or more rows in a longitudinal direction on a longitudinally-long car with tie-beams connecting the struts. A thermal stress relief structure is provided in which the struts arranged upright in the adjacent rows in the longitudinal direction are connected only with tie-beams slanted in a cross direction between the struts, with the thermal stress relief structure preventing warpage or damage of the struts resulting from a bending stress generated in the longitudinal direction at the fixing parts of the struts.