PURPOSE: To prevent leakage of molten metal passed through gap between two counter-rotating rolls in a continuous casting apparatus from the gap opening part side by arranging an approaching effect magnetic field confining device.

CONSTITUTION: Relating to this magnetic field confining device utilizing the approaching effect arranged for preventing the leakage of the molten metal from the opening part side of a gap 35 vertically extended between two members horizontally arranged, this device is constituted of a conductive coil 40 disposed adjoining the opening part side and directly generating the horizontal magnetic field and a nonmagnetic conductor having electrically connecting relation with the surface part of the coil 40. Then, the coil is approached sufficiently to the opening part side, so that the horizontal magnetic field directly generated has the sufficient strength to give the confining magnetic pressure to the molten metal in the gap. In this way, the molten metal can be cast continuously into a slender shape as is.