An exterior structure for a keyboard instrument, which is capable of dramatically increasing the variation of producible types of keyboard instruments while suppressing the cost of molds. A lower case includes a front-side lower case LCf and a rear-side lower case LCr disposed rearward of the front-side lower case LCf in a side-by-side fashion. An upper case UC is disposed above the lower case. The front-side lower case LCf is fastened to the upper case UC, and the rear-side lower case LCr is fastened to the upper case UC, whereby the lower case is secured to the upper case UC.