To provide a sample liquid condensing apparatus capable of efficiently separating a liquid containing particulates to a condensed liquid and a diluted liquid, and to provide a method and an apparatus for measuring the number of particulates in a liquid that uses the sample liquid condensing apparatus.

The sample liquid condensing apparatus 1 is provided with a substrate layered body 2; a raw water head 3, provided for one face of the substrate layered body 2 and a diluted water head 4 and a condensed water head 5 both provided for its another face. The substrate 6 is provided with comb electrodes 16 and 17. Particulates P flow in a downstream direction along the comb electrodes 16 and 17 and gradually shift to the side of a condensed water outlet 10, while flowing though a chamber 9, and condensed water having a high particulate concentration flows out of the condensed water outlet 10.