A method for producing a condensation polymerization reaction polymer, comprising a guide polymerization step in which a molten prepolymer is supplied to the top edge of a wire guide to obtain the condensation polymerization reaction polymer, the wire guide comprising a vertical wire group consisting of a plurality of vertical wires extending in the vertical direction, which are mutually spaced in alignment at an arrangement pitch L1 (mm). In the guide polymerization step, the molten prepolymer aggregates so that a molten prepolymer mass is formed on the vertical wire, and a molten prepolymer mass is formed wherein, the width of the molten prepolymer mass measured in an alignment direction of the vertical wires at a position 200 mm below the top edge being represented as L2 (mm), the width L2 of at least a portion of the molten prepolymer mass satisfies the inequality (1). L1