Abstract: A flow cell having a first plate having a continuous groove formed as a passage on one surface of the plate and having gas/liquid inlet/outlet portions at both the ends of the continuous groove, and a second plate to be kept in contact with said one surface of the first plate, wherein at least either of the first and second plates allows light transmission; fixable reacting substances are fixed on the surface of the second plate, to be kept in contact with the first plate, at plural places corresponding to the continuous groove; and the first and second plates are kept in contact with each other to support each other, for establishing the passage of any one of liquid reacting substances common to the plural fixed reacting substances.