In order to study the dynamic phenomena of electrodeposition of metallic layers, an in situ X-ray diffraction system has been newly developed using an electrochemical cell and an image-plate detector. Electrodeposition of Zn on an Fe(100) single-crystal surface with a current density at 0.5 A cm(-2) was demonstrated in this study. Time-resolved diffraction patterns were obtained by scanning the image plate. It was found that Zn(101) layers were mainly formed from the initial stage of deposition and grew continuously on this substrate. Growth of other layers, such as Zn(103), Zn(110) and Zn(102), were also detected. On the other hand, Zn(100) and Zn(002) were not observed under this condition.