To obtain a continuous particle-size measuring apparatus by which a particle size can be measured with the passage of time by a method wherein a powder which is sampled continuously from the flow of a dry powder and the dispersion medium of a liquid are supplied continuously at room temperature, a dispersion liquid is prepared and the dispersion liquid is supplied continuously to a particle-size analyzer.

A powder is transported in a conveyance pipe 7 by the air so as to be sampled by a suction nozzle 11. The air for instrumentation is made to flow into an ejector 12, and the powder is sucked so as to be supplied to a disperser 2 through a powder supply pipe 21. The flow rate of the air, for instrumentation, which flows in the ejector 12 is adjusted by a valve 13 so as to match the amount of the air, for conveyance, which flows into the nozzle 11. A dispersion medium which is supplied to the disperser 2 by a pump 5 through a dispersion-medium supply pipe 22 forms a whirlpool inside a mixing container 23, the powder is supplied to the whirlpool, and a dispersion liquid 24 is prepared. The dispersion liquid 24 is taken out continuously from a dispersion-liquid discharge pipe 25 so as to be supplied to a sample cell at a particle analyzer 3, and the particle size of the powder which is suspended in the dispersion liquid 24 is measured. Measured data is supplied to a computer 6, and various sampling and processing operations are performed so as to be displayed.