A flow cell includes a housing, a window member, and a pressing member. The housing includes a cell channel in which a sample flows through, has, on at least one end side of the cell channel, an opening communicating with the cell channel, and has a flat surface at an edge of the opening. The window member has a lens portion at a central portion and a peripheral edge portion whose one surface and the other surface are flat. In the window member, one surface of the peripheral edge portion is provided facing the flat surface of the housing so as to seal the opening.