A process for producing an optical disk master, comprises the steps of forming a photoresist layer on a glass master, cutting the photoresist layer by projecting light beam onto the glass master having the photoresist layer thereon to expose the photoresist layer to light, developing the photoresist layer after the cutting step to form a hollow portion corresponding to the light-exposed portion, and carrying out an ion treatment by projecting ions onto the developed photoresist layer to decrease the thickness of the photoresist layer at the developed hollow portion to reach the prescribed depth by the ion-treatment.