To provide technology for assisting performance by a stringed instrument, when a player performs the same operation as normal performance operation.

The stringed instrument includes: a fingerboard on which a string is pressed by fingers of the player; a plurality of frets provided in positions corresponding to the scale of the fingerboard, so that a projection amount from the finger board is variable; a sensor for detecting the distance of the fingerboard from the finger of the player at a position corresponding to the frets; and an actuator in which the projection amount of the corresponding scale is made larger, when the distance becomes a predetermined threshold or less, on the basis of the detection result of the sensor.