PURPOSE: To stabilize a continuous plasma melting and casting operation by calculating the area ratio of melting surface having the fixed temp. value or more and controlling the charging speed of raw material.

CONSTITUTION: In a plasma melting and casting apparatus composed of a plasma torch 1, atmospheric control melting chamber 2, water cooled mold 3, raw material continuously charging device and cast block continuously drawing-down device, the temp. of the melting surface is measured with an infrared ray thermosensor 6. An analyzer 7 for calculating the area ratio occupied with the range having the fixed temp. value or more and a sequenser 8 for deciding the charging speed of the raw material based on the area ratio are provided and further, the plasma voltage is measured, and by changing the automatic drawing-down speed of the cast block, the condition of approaching to the setting voltage is given to a controller 9. By this method, the observation for long time and the manual operation are made unnecessary, and the automation can be executed and the operation is stabilized and product quality is improved.