There are disclosed a method for drying and a method for solid-phase polymerizing a crystallizable polyamide being in an amorphous state which comprises regulating the moisture concentration in the polyamide at its glass transition temperature to at least 0.15% by weight as determined by Karl Fisher titration; heating the polyamide thus regulated at a pressure of at least one arm without reducing the moisture to crystallize the same up to a crystallinity of at least 15% and; further heating the polyamide thus crystallized at a temperature lower than its melting point under reduced pressure with a batchwise heating apparatus. It is made possible according to the method for drying or the method for solid-phase polymerizing the crystallizable polyamide to effect its crystallization without causing tackified sticking or solidified sticking of the polyamide, along with drying or solid-phase polymerization with single apparatus and process, while dispensing with any pretreatment such as surface modification and preliminary treatment equipment intended for crystallization.