To separate a solid component from a sample liquid of the predetermined amount or smaller by filtration while suppressing a loss of the solid component.

A dam part 9 is arranged in a flow passage 3 of a filtration-use miicrochip 1, which is formed on a substrate 2. The dam part 9 is formed to extend from one end 6b to the other end 6c of the direction crossing the flow direction of the flow passage 3. In the dam part 9, a gap 11 smaller than the particle size of the solid component is formed between the dam part and the inside surface 6d of the flow passage 3.