The present invention relates to a method for preparing a green tea extract and, specifically, to a method for preparing a green tea extract using electroconductive plastic catalyst electrodes and to an electrolysis apparatus used therefor, wherein electrolysis is conducted by using metal-free, uncoated, electroconductive plastic catalyst electrodes, thereby allowing hydrogen generated at the minus (-) electrode to be collected in mineral components in the green tea extract and water, so that the dissolved hydrogen time lasts long. The method for preparing a green tea extract of the present invention comprises the steps of: placing collected green tea leaves in an electrolysis apparatus, followed by washing; removing moisture from the washed green tea leaves; steaming the green tea leaves with moisture removed; pulverizing the steamed green tea leaves; and placing the pulverized green tea leaves in the electrolysis apparatus and extracting green tea. The present invention has advantageous effects of: allowing
