A friction stir spot welding method includes a welding step of performing friction stir spot welding of a workpiece by using a pin member and a shoulder member while the workpiece is supported and pressed by the end face of a clamp member and a pressing step of causing a friction stir spot welding device to press an obverse surface and a reverse surface of at least one of a friction-stirred region of the workpiece and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side after the welding step while the pin member and the shoulder member are accommodated in an accommodation space of the clamp member.