A method of producing a cementitious cured body made of a cement composition, wherein the cement composition comprises: cement; silica fume having a BET specific surface area of from 10 m 2 /g to 25 m 2 /g; an inorganic powder having a 50% cumulative particle size of from 0.8 μm to 5 μm; a fine aggregate having a maximum particle size of 1.2 mm or less; a water reducing agent; an antifoaming agent; and water, wherein a ratio of the cement is from 55 vol% to 65 vol%, a ratio of the silica fume is from 5 vol% to 25 vol%, and a ratio of the inorganic powder is from 15 vol% to 35 vol% in a total amount of 100 vol% of the cement, the silica fume, and the inorganic powder, wherein the method comprises: a molding step of setting the cement composition into a mold to provide an uncured molded body; a room temperature curing step of subjecting the uncured molded body to sealed curing or atmospheric curing at from 10°C to 40°C for 24 hours or more, followed by demolding the molded body from the mold, to thereby provide a cured molded body; a heat curing step of subjecting the cured molded body to steam curing or hot water curing at from 70°C to 95°C for 24 hours or more, to thereby provide a cured body after heat curing; and a high-temperature heating step of heating the cured body after the heat curing at from 150°C to 200°C for 24 hours or more, to thereby provide the cementitious cured body. cement; silica fume having a BET specific surface area of from 10 m 2 /g to 25 m 2 /g; an inorganic powder having a 50% cumulative particle size of from 0.8 μm to 5 μm; a fine aggregate having a maximum particle size of 1.2 mm or less; a water reducing agent; an antifoaming agent; and water, wherein a ratio of the cement is from 55 vol% to 65 vol%, a ratio of the silica fume is from 5 vol% to 25 vol%, and a ratio of the inorganic powder is from 15 vol% to 35 vol% in a total amount of 100 vol% of the cement, the silica fume, and the inorganic powder, wherein the method comprises: a molding step of setting the cement composition into a mold to provide an uncured molded body; a room temperature curing step of subjecting the uncured molded body to sealed curing or atmospheric curing at from 10°C to 40°C for 24 hours or more, followed by demolding the molded body from the mold, to thereby provide a cured molded body; a heat curing step of subjecting the cured molded body to steam curing or hot water curing at from 70°C to 95°C for 24 hours or more, to thereby provide a cured body after heat curing; and a high-temperature heating step of heating the cured body after the heat curing at from 150°C to 200°C for 24 hours or more, to thereby provide the cementitious cured body. a molding step of setting the cement composition into a mold to provide an uncured molded body; a room temperature curing step of subjecting the uncured molded body to sealed curing or atmospheric curing at from 10°C to 40°C for 24 hours or more, followed by demolding the molded body from the mold, to thereby provide a cured molded body; a heat curing step of subjecting the cured molded body to steam curing or hot water curing at from 70°C to 95°C for 24 hours or more, to thereby provide a cured body after heat curing; and a high-temperature heating step of heating the cured body after the heat curing at from 150°C to 200°C for 24 hours or more, to thereby provide the cementitious cured body.