To provide an apparatus for concentrating/purifying an enzyme-containing liquid, the constitution of which is simplified and in which the permeate flow velocity through a membrane is kept high by decreasing the accumulation of a cake layer on the surface of the membrane and the clogging of the membrane due to a membrane clogging material.

This apparatus for concentrating/purifying the enzyme-containing liquid is provided with a concentration/separation tank 20 to be filled with an original liquid containing a microbe and an enzyme, an original liquid pump 14 for supplying the original liquid to the concentration/separation tank 20 and an ultrafiltration means 30 and a microfiltration means 40 which are immersed in the concentration/separation tank 20. The ultrafiltration means 30 and the microfiltration means 40 are each a rotary flat membrane type filtration means. A rotary flat membrane constituting the ultrafiltration means 30 and another rotary flat membrane constituting the microfiltration means 40 are arranged to cross each other and rotated in the same direction. The apparatus is provided furthermore with a drainage pump 22 for discharging the remaining liquid concentrated in the concentration/separation tank 20 and a controller 50 for operating each of the means 30, 40 and the pumps 14, 22 sequentially.