The present invention relates to a fluid-controlling device (10) for incorporation into a microchip (100). The fluid-controlling device (10) of the present invention includes: a glass substrate (1b) having a hollow part (3) provided therein, the hollow part (3) having a first opening (3′) extending to a top surface of the glass substrate (1b) and a second opening (4) extending to a bottom surface of the glass substrate (1b); and a glass sheet (2) being 1 to 50 μm in thickness and sealing the first opening (3′), the glass sheet (2) changing a volume of the hollow part (3) when a position of the glass sheet (2) is displaced by and according to a pressing force applied toward the hollow part (3). With use of the present invention, it is possible to provide a versatile microchip system being usable under a high pressure and being usable with an organic solvent.