A string-striking device for a piano, where a static loading acting on a fore-end on the playing side of a key can be easily adjusted. A long weight lever (21) is provided on each key (3). The lever (21) is installed along the length direction of the key 3, on an upper part on the side opposite the playing side of the key (3). The installation is made such that one end of the lever (21) is vertically pivotably fixed to a piano body and the vertically displaceable free-end side of the lever is in contact with the upper face of the key (3) by its own weight to apply a load on the key (3). The structure above enables a static load on the key (3) to be adjusted by replacing the lever (21) without disassembling the string-striking device and removing the key (3).