An evaluation apparatus of scientific phenomena, including: a base plate of a plate-like body on whose surface is formed an elongated groove having a transversely cross-sectional area of not more than 1 mm.sup.2; and a cover plate that is disposed on a surface of the base plate in close contact therewith and forms a fine flow passage on the base plate by covering the elongated groove, wherein scientific phenomena in the fine flow passage can be visually recognized.