A friction stir spot welding method of welding a workpiece by friction stir spot welding using a friction stir spot welding device including a rotary tool that partially stirs the workpiece and a clamp member (8, 18, 28) that presses the workpiece, the rotary tool including a pin member that rotates around a predetermined axis and is provided so as to be able to advance and retract in a direction of the axis and a shoulder member that rotates around the axis while surrounding an outer periphery of the pin member and is provided so as to be able to advance and retract in the direction of the axis independently of the pin member, and the clamp member (8, 18, 28) having an inner peripheral surface (8b, 18b, 28b) that forms an accommodation space for the pin member and the shoulder member so as to surround an outer periphery of the shoulder member and an annular end face (8a, 18a, 28a) configured to come into surface contact with the workpiece, the friction stir spot welding method comprising: a welding step of performing friction stir spot welding of the workpiece by using the pin member and the shoulder member while the workpiece is supported and pressed by the end face (8a, 18a, 28a) of the clamp member (8, 18, 28); characterized in that the method further comprises: a pressing step of causing the 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 having undergone friction stir spot welding and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side to the rotary tool after the welding step while the pin member and the shoulder member are accommodated in the accommodation space. the rotary tool including a pin member that rotates around a predetermined axis and is provided so as to be able to advance and retract in a direction of the axis and a shoulder member that rotates around the axis while surrounding an outer periphery of the pin member and is provided so as to be able to advance and retract in the direction of the axis independently of the pin member, and the clamp member (8, 18, 28) having an inner peripheral surface (8b, 18b, 28b) that forms an accommodation space for the pin member and the shoulder member so as to surround an outer periphery of the shoulder member and an annular end face (8a, 18a, 28a) configured to come into surface contact with the workpiece, the friction stir spot welding method comprising: a welding step of performing friction stir spot welding of the workpiece by using the pin member and the shoulder member while the workpiece is supported and pressed by the end face (8a, 18a, 28a) of the clamp member (8, 18, 28); characterized in that the method further comprises: a pressing step of causing the 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 having undergone friction stir spot welding and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side to the rotary tool after the welding step while the pin member and the shoulder member are accommodated in the accommodation space. a welding step of performing friction stir spot welding of the workpiece by using the pin member and the shoulder member while the workpiece is supported and pressed by the end face (8a, 18a, 28a) of the clamp member (8, 18, 28); characterized in that the method further comprises: a pressing step of causing the 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 having undergone friction stir spot welding and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side to the rotary tool after the welding step while the pin member and the shoulder member are accommodated in the accommodation space.