We developed a scanning tunneling microscope (STM) operating below 2 K in a vacuum of less than 10(-8) Pa. This STM was constructed to study low-temperature properties such as superconductivity and charge density waves in artificial material on surfaces. The sample is prepared in an ultra-high-vacuum preparation chamber separated by a gate valve from the STM chamber, and is transferred to the microscope which is attached to a liquid He pot. By pumping liquid He, the sample is cooled down to 2 K. At low temperature, we observed an atomic image of graphite surface with its constant current mode, and an superconducting gap of Pb film with its tunneling spectroscopy mode.