Influence of gelatin on the electrode process of some developing agents, i. e., hydroquinone, Metol, Phenidone and ascorbic acid was investigated by potentiostatic chronoamperometry at the rotating gold disc electrode. The oxidation of Phenidone was little affected by gelatin. But the inhibition effect by gelatin became more remarkable in the order Metol, hydroquinone and ascorbic acid, and in the last case the oxidation was inhibited almost completely in a short period after the beginning of electrolysis. The rotation speed dependence of the decrease in the anodic current density of ascorbic acid suggested the adsorption of gelatin, the rate of which is controlled by diffusion. The area required for an adsorbed gelatin molecule. was calculated. On the other hand, the wave height of the current density-potential curves in Phenidone solutions containing ascorbic acid and gelatin, increased in proportional to the Phenidone concentration and the square root of the ascorbic acid concentration. This suggested the regeneration of Phenidone radical by ascorbic acid and the discriminated charge transfer through adsorbed gelatin between these two developing agents.