To provide a seat fastener capable of easy detachment though it achieves sure fixation of a seat cushion to a floor panel and to provide the seat fastener made of a synthetic resin, which can be used by being buried in a pad member regardless of the presence/absence of a metallic frame and make it possible to lighten the pad member.

For the seat fastener 24 of this invention, the whole is formed of the synthetic resin and a flat movable piece 35 having a base part 35a on the front end side is provided on the front end part of a pillar part 31 forming the base body. The movable piece 35 is provided with a pawl part 36 to be hooked to the lower surface of the floor panel 27 of a vehicle, and also the part other than the base part of the movable piece 35 is separated from the pillar part 31 through a slit 34. Then, the movable piece 35 is extended further from a position where the pawl part 36 is formed and a pressure receiving part 20 is formed there.