Abstract: A touch signal probe for electrically detecting the contact of a touch pin with a work to be measured in all three-axes directions. The apparatus can be attached to a three-dimensional coordinate measuring system to automatically detect electrical touch signals indicative of the contact with the work. The internal structure of the probe case is constructed such that a three dimensionally movable support can be attached thereto to provide a touch pin base which is movably supported on seats fixed on the probe case which carries the touch pin by means of a Z-axis movable support mechanism. The Z-axis support mechanism consists of a pair of diaphragms fixed on the upper and lower ends of the touch pin base at their peripheries respectively and a support shaft rigidly connected with the central portions of the diaphragms and holding the touch pin at its lower end.