There is provided a part holding head assembly of a part mounting device including: a rotary head; a spindle configured to rotate in a first direction T with respect to a central axis of the spindle and configured to move in a second direction Z substantially parallel with an extending direction of the central axis of the spindle; a nozzle provided at a first end of the spindle; a raising part configured to move the spindle to in the second direction Z; and a contact detecting sensor configured to sense the nozzle contacting a part or the part held by the nozzle contacting a substrate and configured to generate a contact sensing signal according to the sensing.