PURPOSE: To improve the dispersibility of fibers and moldability and to shorten the time from curing till the end of the painting time by subjecting a specific mixture composed of cement, inorg. filler, synthetic fibers and water to dehydration pressing and curing under specific conditions, then painting and drying the surface of the hardened body.

CONSTITUTION: The mixture is obtd. by mixing, under oscillation, 100 parts cement, by weight, 200 parts inorg. filler such a fly ash and/or silica sand, 0.3-10 parts synthetic fibers consisting of short fibers, ≥27 parts water and if necessary, ≤10 parts water soluble polymer material. This mixture is subjected to the dehydration pressing under ≥50kg/cm2 face pressure by which the sheet is molded. The sheet is cured under the curing conditions of ≥80% relative humidity at 35-55°C, ≤25°C/hour heating up rate from room temp. up to the max. temp., and within 12 hours total curing time in an incomplete hermetic chamber at least part of which is opened to the atm. The surface of the hardened body obtd. in such a manner is then subjected to the painting and drying. The curing conditions specified to 56-75°C, ≥80% relative humidity, ≤35°C/ hour heating up rate, within 10 hours total curing time or 76-90°C, ≥80% relative humidity, ≤45°C/hour heating up rate and within 8 total curing time are equally satisfactory.