Provided is a defect judging unit for a measuring probe including: a stylus; four detection elements; and a signal processing part. The defect judging unit includes a defect judging part configured to compare four judged signals corresponding to the generated signals with predetermined thresholds when the object to be measured and the contact part are out of contact with each other and judge that a defect exists if any of the judged signals is greater than the predetermined threshold, and a judged result output part configured to output a judged result of the defect judging part. According to this configuration, the defect judging unit of the measuring probe and the defect judging method thereof capable of ensuring measurement reliability with a simple configuration are provided.