An In-Situ gel casting machine comprising a gel casting stand (1), a rubber cushion (2), and a locking base (3). Overlapping a notched glass (121) with a glass plate (122) tightly together will form a gel room (123), it is called as the slab gel casting mold (12). Put the same two slab gel casting molds (12) into each side of the portable casting stand (11) along its insides, and then insert the wedge frames (13) against each slab gel casting mold (12), which will form the gel-casting stand (1). Because each sidewall locking structure (32) of the locking base (3) compresses the slab gel casting molds from two directions, it ensures that the slab gel casting molds are sealed well. Without moving the slab gel casting molds, an electrophoresis experiment can be started right after the gel has been solidified, which can avoid the leakage of the gel solution and the production of air bubbles into the slab gel casting molds.