A detecting device for detecting the positions where strings are operated, and an electronic musical instrument using the detecting device, such as an electronic stringed instrument or an electronic keyboard instrument, wherein each of frets, with which conductive strings are brought into contact, is formed of a two-layer structure of a conductive member and a resistance member provided on the conductive member. Voltage pulses are sequentially applied to either the conductive strings or the conductive members of the frets and a voltage pulse is detected from a conductive member or a string, thus detecting a position in which a string is stopped against the fret.