To provide a batch controller which supplies main fluid and sub-fluid at a prescribed mixing ratio.

This batch controller is constituted by connecting a main fluid supply route 10 for supplying the main fluid at a set flow rate to a main storage tank 11 and a sub-fluid supply route 20 for supplying the sub-fluid to a sub- storage tank 21, connecting a preset counter 1 for setting an arithmetic value and integrating and displaying the supply rate of the fluid to a main flowmeter 13 and a sub-flowmeter 23 and building a batch treatment control unit, which repetitively computes the arithmetic value of the sub-fluid with respect to the flow rate of the main fluid an emits a supply completion signal to a main pump 12 and a main automatic valve 14 when the main fluid attains a set flow rate, and to a sub-pump 22 and a sub-automatic valve 24 when the arithmetic value is attained, in the preset counter 1 and, therefore, the inputting of the arithmetic value, such as the mixing ratio or the mixing concentration, as it is, merely necessitated and the shorter time is needed for the setting work. There is no need for computing the supply rate of the sub-fluid at every change of the computed value, and the occurrence of an error in calculation is averted.