Micropattern formation on ZnO thin films has been carried out using a photodissolution reaction. ZnO thin films were prepared on glass and on transparent, conductive SnO2-coated glass by spray pyrolysis. The dissolution rates of the ZnO films were measured under illumination (v(light)) and in the dark (v(dark)) under various conditions. The v(light) and v(dark) values were determined by measuring the zinc content in the ZnO film before and after the dissolution reaction using x-ray fluorescence spectroscopy. The dissolution rate became larger under UV illumination under various conditions. Both v(dark) and v(light) depended strongly on the pH value of the electrolyte solution and the bias voltage. The best conditions to form Under the best conditions, a micropattern the ZnO film micropattern were determined by measuring both v(light), and v(dark). was obtained on the ZnO thin films on SnO2-coated glass substrates under illumination through a photomask. The linewidth of the micropattern can be as low as about 130 mu m.