PURPOSE: To change the mixing ratio of liquid optionally with simple operation by controlling the operating time of a constant volume pump or a constant pressure feeding apparatus and a fixed interval orifice with a timer which can change setting time.

CONSTITUTION: A liquid surface controller 2 makes a constant volume pump 5 drive to start the feeding of the mixture consisting of 2 liquid components and over or liquid A and solid B to a stock and mixing tank 1. A mixer 4 agitates the mixture and a tank 1 stocks the agitated mixture. A timer which is set on a control board 11 and assigned to each liquid stops the feeding of each liquid. The mixing ratio can be optionally changed by selecting the setting time of the timer suitably. The mixing ratio can be changed only by a single operation and it is also unnecessary to increase liquid feeding pressure.