PURPOSE: To measure automatically contact resistance and rotation noise by using a constant current power source as a power source for measuring the contact resistance and rotation noise, and finding the value the contact resistance of a body to be measured by a voltage drop method.

CONSTITUTION: A constant current power source 22 is used as the power source for measuring the contact resistance and rotation noise and the contact resistance value of a body 1 to be measured is found by the voltage drop method. The use of the constant current power source 22 improves measurement precision and an observed voltage V0 and the contact resistance value of the body 1 to be measured are in proportional relation, so the calculation of the contact resistance is easy. Artificial resistances R1WRn having discriminating values for the contact resistance are incorporated in a measuring circuit, so the discrimination level of the contact resistance value is inputted easily to a computer 16 and further to an electromagnetic oscilloscope 24.