A method and apparatus for detecting the presence of mis-stripping uses a sensor function section free from operation sensibility variation or destruction due to vibration, impact or the like. Only a ram head in a punch press is provided in an electrically insulated state on the machine side and a low voltage is applied to the ram head. Grounding and conduction of the ram head to the machine side through punch tools is detected when the ram head is in contact with the punch tools, nonconduction is detected when the ram head and punch tools are not in contact, and the nonconduction time is determined to be mis-stripping.