PURPOSE: To easily manufacture a high precise trough having high durbility by integrally forming the trough body having U-shaped cross section with ceramic and coating heat insulating exterior at the outer side.

CONSTITUTION: The trough body 1 having U-shaped cross section is formed of the ceramic. This trough body 1 is manufactured by setting a core into an outer mold manufactured by the preset shape dimension and filling the water- kneaded ceramic into gap part between the outer mold and the core and removing the mold after solidifying. After heating and drying the formed trough body 1, the ceramic paper 2 is stuck to the outside wall of the trough body 1 and a heat insulating plate 3 (ceramic fiber-made) is set to this outer side. By filling the dry powder into gap between the ceramic paper 2 and the heat insulating plate 3, a buffering layer 4 is formed, and after sticking the ceramic paper 5 at the outside of the heat insulating plate 3, by sticking the exterior plate 6 at the outer side, the trough product 7 is completed. By this method, the highly precise trough having uniform quality and the prescribed property can easily be manufactured.