PROBLEM TO BE SOLVED: To accurately acquire flow rate of slurry using a flow meter of a type that is not appropriate for flow measurement of the slurry.SOLUTION: A slurry pressure feed unit 5 (slurry supply device) supplies iron powder slurry accumulated in a slurry accumulation unit 21 while adjusting the flow rate. The slurry pressure feed unit 5 includes: a thickening liquid accumulation unit 22 (comparison liquid accumulation unit) for accumulating thickening liquid (comparison liquid for measurement) whose property affecting the pump delivery is aligned to the iron powder slurry; a two-liquid interlock type pump 23 for delivering the iron powder slurry accumulated in the slurry accumulation unit 21 and the thickening liquid accumulated in the thickening liquid accumulation unit 22 under the same condition with separate systems; and a thickening liquid flow meter 42 for measuring the delivery flow rate of the thickening liquid.
