A hammer device for a keyboard instrument, enabling improvement of efficiency and yield, in manufacturing weights to be attached to each hammer body while suppressing an increase in manufacturing cost. Each hammer includes a hammer body having a weight mounting portion, a common weight attached to one of left and right side surfaces of the weight mounting portion, and an adjustment weight having a length set according to a touch weight required by the associated key and attached to the other of the left and right side surfaces of the weight mounting portion. A chassis has a plurality of partition parts, and on the left and right surfaces of the hammer body, there are formed left and right opposed protrusions, respectively, each of which protrudes outward of the weight and is opposed to a partition part associated therewith via a predetermined clearance.