A flat plate-like space region 13A formed between an inflow port 11A and an outflow port 11B of liquid has a predetermined thickness, and the planar shape of the space region 13A is configured in a shape in which the surface tensions generated, by liquid supplied to the space region 13A, from different places in a contour portion of the space region 13A toward the inner side of the space region 13A interact with each other. Thus, when the liquid is supplied to the space region 13A of a liquid film generating tool 100A from the outside, the liquid spreads in a plate shape along the shape of the space region 13A, and the surface tensions generated toward the inner side of the space region 13 can interact with each other to form a liquid film.