To provide a method for manufacturing an Al-Zn alloy plated steel sheet, in which a processing cost can be greatly reduced and workability of the plated steel sheet can be improved by simply performing a post-annealing treatment.

An Al-Zn alloy plated steel sheet is wound into a coil to form a coiled steel sheet 1, which then is housed inside a furnace body 3 of a batch-type annealing furnace 2 and is heated until the temperature of the outside surface of the coil reaches 280-360°C. Subsequently, the coil is immediately cooled at a cooling rate of ≤1°C/min, and while the coiled steel sheet 1 reaches a low temperature, deposition of Zn in an Al-rich phase is promoted by heat of the coiled steel sheet 1 itself, thereby modifying and softening a plating layer.