A buckle device 10 for a seat belt includes: an anchor plate 11 that can be attached to a vehicle body side; a buckle 20 to which a tongue of the seat belt can be detachably attached; and a woven fabric 30 that is passed through hole portions 14, 26 formed respectively in the anchor plate 11 and the buckle 20, the woven fabric 30 being folded back so as to overlap at least triply and being sewn together in the overlapping part. A tip end portion 31a of the woven fabric 30 tucked into the inner side contacts the opposing buckle 20.