This invention relates to a processing liquid circulation apparatus which can keep constant effective supply quantities of the processing liquid to a work bed while controlling variably the flow rates of the processing liquid supplied to a discharge machining zone, and which is moreover economical. The supply quantities of water have the processing liquid which is jetted to the discharge machining zone and to the work bed (12) through upper and lower nozzles (15, 16) and a spray (35) communicating with conduits (32b ∩ 32e) branched into two routes from a conduit (32a) connected to a tank (31) are regulated by a flow rate regulation valve (34) so that the two route supply quantities are inversely proportional to each other but their sum can be maintained. In rough machining, the jet quantity of water through the nozzle increases while the jet quantity through the spray decreases and at the time of shift from this rough machining to finish machining where the jet quantity through the nozzle decreases but the jet quantity through the spray increases, the effective supply quantity of water to the work bed from both the nozzle and the spray does not change so that any thermal deformation does not occur substantially, hence deformation of the work (40) and eventually, the change of the relative position between the work and a wire electrode (50), are prevented and the discharge machining can be conducted highly accurately.