PURPOSE: To increase number of identifications without increasing in size an apparatus by providing marker slide contact means for selecting a predetermined marker from a plurality of markers to move in slide contact marker parts of individual markers to a work in an inherent moving mode.

CONSTITUTION: A right side switching cylinder actuator 28 of a base plate 13 is, for example, extended to remove and hold a sealing cap 31 engaged with a red-colored marker pen MKP. Then, a pressing cylinder actuator 20 is extended to bring a tip CP of a red-colored marker pen MIP into contact with an outer surface WF of a cylinder block W. When the contact is confirmed, an oscillatory cylinder actuator is extended and retracted to slightly reciprocate to oscillate the plate 13 around an axial center of an oscillator shaft, then the tip CP is moved down in slide contact with an outer surface WF to put a red identification mark at a position on an extension line of a centerline CL of the plate 13. Similarly, an identification mark of a different mode is marked by a blue-colored marker pen disposed at a left side of the plate 13.