Screw supporting device and screw tool

The invention relates to a screw supporting device used for assisting a screw tool in locating a screw. The screw tool is provided with an output shaft axis. The screw supporting device comprises a shell, a drive piece and at least one supporting unit capable of supporting the screw, wherein the drive piece is located in the shell and connected with the screw tool, and the drive piece responds to the screw tool to abut against a workpiece through the screw in the direction of the output shaft axis and drives the supporting unit to move to the position where the screw is supported. According to the screw supporting device, axial abutting force generated when the screw abuts against the screw tool is utilized for making a supporting mechanism for supporting the screw automatically support the screw.