To provide a rubber molding device capable of stably molding a rubber member having a uniform shape by sufficiently dispersing heat generated at the time of warming processing to keep the temperature of a rubber uniformly.

The rubber molding device to warm kneaded rubber by an open roll 11, and thereafter, to mold the rubber into a predetermined shape is provided with a division guide plate 12 for dividing the open roll 11 in the width direction into a production side area at which warming of the kneaded rubber is performed and a preparation side area at which preparation for rubber changing is performed and is constituted so that the division guide plate 12 is moved in the production side area by the pressure force of kneaded rubber supplied to the preparation side area when the rubber is changed to cause the preparation side area and the production side area to perform switching. The moving range of the division guide plate is configured to satisfy 0.5<L1/L≤0.9 ( where, L represents the full width of the open roll, and L1 represents the roll width of the production side area).