A coaxial connector for microwave and millimeter wave measurement can be used by attachment to a vacuum chamber for instrumentation when measuring a high frequency characteristic for various electronic devices at low temperature. The coaxial connector connects microwave instrumenting equipment to a device to be tested within vacuum chamber (e.g., so as to measure a low temperature and high frequency characteristic for a high frequency device). It includes a support plate for attachment to the vacuum chamber and a support screw to prevent the coaxial connector from rotating. The support screw is of hexagonal shape in the exemplary embodiment and is arranged to one side on the center of the support plate. A coaxial cable transmits the measured signal and is extended to pass through the center of the support plate and support screw, and a V-shape connector on each end of the cable for respectively coupling between a fixed sample stand in the vacuum chamber and the microwave instrument equipment.