A melting apparatus having a compact structure, of economical equipment cost, enabling to vacuum melting and refining at high productivity. A metal melting apparatus has a structure in which a refractory furnace wall 12 is furnished on an outer circumference thereof with a seal jacket 16 of air tight and non-electrical conductivity, and disposed with vertical water cooling copper pipes 47 along the inner circumference of the seal jacket 16 at predetermined space, and the furnace casing 10 is arranged at the outer part to encircle the furnace casing with an induction heating coil 38, and the furnace casing 10 is secured to a frame 42 by means of the seal jacket 16 for reinforcing the structure. The seal jacket 16 of the furnace casing 10 is fixed to the frame via an upper flange 44 and a lower flange 28.