PURPOSE: To reduce the cost of equipment by simplifying a system line of an automatic compounding device.

CONSTITUTION: The material supply lines B1-B3 are connected to a compounding tank BT, and the stock tanks ST1-ST3 stock individually plural types of compositions compounded in the tank BT. The tank BT is connected to each tanks ST1-ST3 via the compound lines S1-S3 for the individual transfer of those compositions. The remaining compositions of the tanks ST1-ST3 are detected by the automatic control, and the amount of materials supplied to the tank BT through each supply line is set for compounding the same compositions as those of the stock tanks having the small remaining amounts. At the same time, the compound lines led to the stock tanks having the small remaining amounts are selected and switched to each other for transfer of the compositions stores in the tank BT. Then, a fixed quantity of compositions compounded in the tank BT are supplied to the stock tanks having the small remaining amounts.