The two-step electrolysis technique was developed for the purpose of preparation of a transparent and conductive zinc oxide (ZnO) film by cathodic deposition from a simple zinc nitrate aqueous solution at ambient temperature. The structural, optical, and electrical characterizations were performed with an atomic force microscope, scanning electron microscope, reflection high-energy electron diffraction, X-ray diffraction, measurements of optical transmission and absorption spectra, and Hall measurement. The purpose was achieved by using a two-step electrolysis consisting of first-step electrolysis at -1.2 V referred to an Ag/AgCl electrode for electric charge of 0.03 C cm(-2) and of second-step electrolysis at -0.7 V. The first-step electrolysis gave homogenous deposition of ZnO particles over an entire substrate surface. During the second-step electrolysis the ZnO particles grew normal to the substrate surface, and the resultant ZnO film did not contain any defects such as pores and showed smooth surface. The ZnO film showed high optical transmission of about 80% in the visible light region and resistivity as low as 4 x 10(-3) Omega cm with 6.5 x 10(19) cm(-3) carrier concentration and 23.7 cm(2) V-1 s(-1) mobility.