The astrometric satellite Gaia has recently released part of its third data set, which provides a good opportunity to hunt for more open clusters in the Milky Way. Here, we conduct a blind search for open clusters in the Galactic disk using a sample-based clustering search method with high spatial resolution, which is especially suited for finding hidden targets. In addition to confirming 1930 previously known open clusters and 82 known globular clusters, 704 new stellar clusters are proposed as potential open clusters at Galactic latitudes of |b|<=20{deg}. For each of these new open clusters, we present its coordinates, detailed astrometric parameters and age, as well as its radial velocity, if available. Our blind search greatly increases the number of Galactic open clusters and shows the incompleteness of open cluster census in our Galaxy.