Abstract: This invention discloses an ozone generator having a simple structure and little mechanical trouble, whereby ozone gas is generated directly in water or stagnant solutions having a high electric conductivity without any blower or bubble generating device, including one or more pairs of electrodes being submerged in liquids, the electrodes being made with metals resistant to oxidation such as platinum, the shape of said electrodes being formed in a strip line type and on an insulator substrate, the spacing between said electrodes being set to be of 0.02 to 1 mm, a square wave voltage with positive and negative pulses are supplied to said electrodes, thereby build-up of impurity in liquids to said electrodes being prevented, thus high concentration of ozone O.sub.3 generated effectively by combining O with O.sub.