We constructed a low temperature (LT) ultrahigh vacuum (UHV) atomic force microscope (AFM) system using a frequency modulation (FM) technique. As the displacement sensor, we used a lead zirconate titanium (PZT) cantilever to detect the force interaction between the tip and sample. Although the PZT film can be used as the actuator to oscillate the cantilever, an external piezoactuator is used to oscillate the PZT cantilever for small oscillation amplitude stably. The PZT cantilever does not require any alignment mechanisms for displacement detection and does not have thermal source due to resistive heating. Therefore, it is one of the promising force sensors under LT environments. Attractive force interaction was detected by the PZT cantilever. We presented the preliminary result of imaging of atomic steps on Si(lll) surface measured by noncontact-AFM at room temperature and LT environment.