The present invention reduces temperature gradient in the direction of the radius of solidified ingots of silicon immediately after solidification, which has serious influences on the quality as a solar cell and improves the quality. Silicon raw materials are melted inside a bottomless crucible combined with an induction coil by electromagnetic induction heating. The silicon melt formed inside the bottomless crucible is allowed to descend and solidified ingots of silicon are manufactured continuously. Plasma heating by a transferred plasma arc torch is also used for melting the silicon raw materials. The plasma arc torch is moved for scanning along the inner surface of the bottomless crucible in the horizontal direction. A plasma electrode on the solidified ingot side to generate transferred plasma arc is allowed to contact the surface of the solidified ingot at positions where the temperature of the solidified ingot becomes 500 to 900 C.