As the scale of microelectronic engineering continues to shrink, interest has focused on the quantum nature of electron transport through quantum wires and/or carbon nanotubes and electron storage on quantum dots. We report here firstly measurements of the quantized conductance of metal quantum poin contacts (QPC's) prepared with an STM that we can simultanelusly image using ultra-high vacuum (UHV) electron microscope. This STM-UHV electorn microscope technique allows us to directly observe any relationship between the structure and conductance of the QPC's. We observed gold metal QPC's, and found a single chain of gold atoms suspended between the electrodes. We can thus confirmed that the conductance of a single strand of atoms is 2e@super 2@/h, (13k@ohm@)@super -1@ , where 'e' is the electron charge and 'h' is Planck's constant. The QPC's often can form a very long nanowire suspended between the electrodes, which are ideal one-dimensional channel similarly to carbon nanotubes. To verify structures of such long matal wires, we made stable nanowires by electorn beam irradiation onto a very thin gold film. We first obtained high-resolution images of a linear chain which consists of four suspended gold atoms. The gold atoms had anomalous spacing compared with the nearest neighbor distance of the bulk crystal. Second, the nanowire which appears as three or four atom rows the diameter in TEM images have a structure different from the bulk crystal. It is very promising for microelectronic engineering that long gold nanowires have thier own specific structure and, thus, have definit conductances specific to their structures. @FootnoteText@ H.Ohnish, Y.Kondo, and K.Takayanagi, Nature, 395 (1998) 780.