Requirement for precision measurement becomes extremely advanced as industrial needs advances. CMM (Coordinate Measuring Machine) is one of the most adequate measuring machines to meet the requirement. As the precision of CMM becomes higher, it is important to improve the sensitivity of probe. We developed a contact type probe which consisted of a QPD (quadratic photo diode), a ball lens, and a laser diode to detect the displacement of stylus. The probe system has a resolution of 31nm.