Provided is a stringed instrument using frets, in which a low-pitched sound range is extended without changing the size of the main body and the sound range before the low-pitched sound range has been extended can be restored by using a capotasto. The stringed instrument comprises: a high-pitched sound string nut which is attached to an end of a fingerboard and from which a low-pitched sound string portion is removed; a low-pitched sound string nut attached at a position selected so that the string length from a saddle extends over the position of the high-pitched sound string nut; a new fingerboard provided over the area extending to the low-pitched sound string nut from the portion where the low-pitched sound string portion of the high-pitched sound string nut is removed; a minus-one fret and a zero fret newly provided on the fingerboard; and a board used for attaching a capotasto for always pushing the low-pitched sound string against the zero fret and provided on the headstock side in the vicinity of the high-pitched sound string nut.