PURPOSE: To produce a polyamide reduced in water absorbency without lowering mechanical strengths by simultaneously performing the polymerization and molding of -caprolactam by heating in the presence of a specified alkali catalyst and a promoter.

CONSTITUTION: -Caprolactam is mixed with an alkali metal lactamate in an amount of 0.3-2.5mol% based on the total amount of the -caprolactam used in the polymerization and molding and in such an amount that the amount of polyamide oligomers in the alkali metal lactamate is 0.5wt.% or below based on the -caprolactam used in the polymerization and molding, and also with at least one promoter selected from an at least bifunctional aliphatic isocyanate and carbamide lactam and used in an amount to give an equivalent ratio of the alkali catalyst to the functional groups of the promoter of 0.5-3.0. The obtained mixture is agitated at 70-130°C and filled into a mold heated to 130-190°C to effect polymerization and molding for 2-10min.