PROBLEM TO BE SOLVED: To provide a feeder including a screw with excellent wear resistance and low cost. SOLUTION: The feeder includes a cylindrical portion 31 having an introducing hole 31A into which a culture medium B is fed and a discharging hole 31B which discharges the culture medium B at its both end sides respectively, and a screw 33 inserting in the cylindrical portion 31 and having blades 33A and 33B for moving the culture medium B from the side of the introducing hole 31A to the side of the discharging hole 31B by its rotation, and the blade on the side of discharging hole 31B is made thicker than that of the introducing hole 31A in the blades 33A and 33B.
