Wind instrument includes a tubular body having a plurality of tone holes, and a plurality of keys capable of opening and closing the tone holes. Via a retaining member, detector units are provided within the tubular body in corresponding relation to the keys, and each of the detector units is generally opposed to the back surface of the corresponding key. Each of the detector units detects a relative distance to the back surface and outputs an electrical signal, on the basis of which an opening/closing state of the key can be detected. The retaining member, accommodated in the tubular body, positions and retains each of the detector units in such a manner that the keys and tubular body and the individual detector units are kept in non-contacting relation to each other.