PURPOSE: To make a key switch to have a security function, so as to make keys in common, reduce the number of keys, and restrict the position selection for every personnel.

CONSTITUTION: A holding body 11 is provided with a first rotation angle range specification groove 12 and a second rotation angle range specification groove 14 shifted in its axial direction. The specified rotation angle range θ2 of the second rotation angle specification groove 14 is made to include the special angle range outside the specified rotation angle range θ1 of the first rotation angle range specification groove 12. And, a holding body 11 is provided with a horizontal groove 18 in which the projection part 31 of a key 30 can reciprocate between the first and second rotation angle range specification grooves 12 and 14 when a selected rotation angle is θx. A switch signal output switch 40 is so constituted that the special switch signal different from the switch signal can be output when a rotation body 21 is rotated, within the range of the special angle range, latches 11 and 12 have their security functions, and only an operator who knows the security by means of a single key 30 except to the switch signal using the key 30 is allowed to use the key 30 so that the special switch signal can be selected and output.