Provided is a method that, when pulp fibers are recovered from used absorbent articles that have been put into collection bags, makes it possible to safely and sanitarily crush the used absorbent articles while suppressing costs. A method for recovering pulp fibers from used absorbent articles, the method comprising: a crushing step (S12) in which collection bags (A) in which used absorbent articles have been sealed are put into a container (65), the collection bags in the container are transferred to a crushing device (12) that communicates with the container, and, bag by bag, the crushing device crushes the used absorbent articles in the collections bags in a deactivating aqueous solution; and a separation step (S13) in which the pulp fibers, a highly water-absorbent polymer, and the deactivating aqueous solution are separated from the crushed product and deactivating aqueous solution obtained in the crushing step.