A hammer unit for use in a keyboard device or the like includes a plurality of hammer arms which are respectively operated in response to key depression operations on a plurality of keys, and a hammer connecting section which has a length corresponding to array of the plurality of keys, is connected to the plurality of hammer arms to support the plurality of hammer arms in an arrayed state, and has mounting sections which are provided in a direction of the array in areas where the hammer arms are not connected, and by which the hammer connecting section is mounted to a keyboard chassis. As a result, the assembling workability is improved.