The invention provides a microinjection apparatus for a fluid. The microinjection apparatus includes a substrate, a manifold, a fluid chamber, a dummy chamber, a detecting device, and a pair of parallel conductive plates. The manifold is formed on the substrate and supplies the fluid chamber and the dummy chamber, also formed on the substrate, with the fluid. In addition, the pair of parallel conductive plates are formed on a pair of opposite inner walls of the dummy chamber, and electrically connected to the detecting device. By applying the pair of parallel conductive plates and the detecting device provided in the invention, the size of the fluid chamber and the fluid-filled condition relative to the fluid chamber can be indirectly detected by non-destructive testing. Furthermore, the cost of and the time of testing also can be prominently saved.