PURPOSE: To provide a method capable of continuously extruding and forming a cement molded plate superior to a mechanical strength at a proper viscosity.

CONSTITUTION: In a manufacturing method of the cement molded plate formed by extruding and molding a cement containing W/O type emulsion composition consisting of cement (A), water (B), a vinyl monomer (C), a reverse emulsifier type emulsion (D), and a higher fatty acid of 8-24 carbon numbers (E), a weight ratio of the cement (A) and the water (B) is 100:(10-50), the reverse emulsifier (D) being a neutralized product of an amino group containing condensation reaction product (d1) and an organic sulfonic acid and/or an organic acid phosphate (d2), and the higher fatty acids (E) of 8W24 carbon numbers are added 0.05-1.5 parts wt. for the total 100 parts wt. of the water (E), the vinyl monomer (C), the reverse emulsifier (D) and the higher fatty acid (E). Such a cement molded plate manufacturing method and a manufacturing method for cement molded plate further incorporated an organic or inorganic reinforcing agent (F) in the emulsion composition are covered.