Provided is a button fastener-side die (40), on which a button fastener (20) is to be set when a snap member (10) is attached to a fabric (1) with the button fastener (20). The button fastener (20) comprises an annular base (21) defining an opening (23) and a plurality of legs (22). The button fastener-side die (40) comprises: a holding part (70) for holding the button fastener (20) and a correcting member (61) for passing through the opening (23) of the button fastener (20) held by the holding part (70), a pushing member (63) for pushing the correcting member (61) to move in a passing direction toward passing through the opening (23) of the button fastener (20), and a first spring (62) disposed between the correcting member (61) and the pushing member (63). When at least one of the legs (22) of the button fastener (20) is in an abnormal position, the correcting member (61) corrects the abnormal leg(s) (22b) to be in the normal position as the correcting member (61) is passing through the opening (23). When the pushing member (63) is in its forefront position, the correcting member (61) reaches its forefront position by the first spring (62), where the correcting member (61) can contact the fabric (1).