PURPOSE: To produce an article controlled in dyeability or a terminal amine group content by comparing the measurement of the dyeability or terminal amine group content of an article performed at periodic intervals with its desirable standard point and pouring a diamine at a specified injection rate according to the deviation from the standard point.

CONSTITUTION: In a method for controlling the terminal amine group content or dyeability of a polyamide article produced from a molten polyamide stream, the measurement of either the dyeability of the article or the terminal amine group content of the article is performed at periodic intervals, the obtained measurement is compared with the standard point representing the desirable dyeability or terminal amine group content of the article, and a diamine is injected into the molten polyamide stream at an injection rate shown by the formula according to the deviation of the measurement from the standard point. The correction coefficient in the formula is determined by a test so as to obtain a polyamide article having a terminal amine group content changed as a result of mixing the polyamide with the diamine.