PURPOSE: To shorten a lead time by executing cutting of a feeder head, refining, machining and inspection after sequencial heat treatment, after casting a work.

CONSTITUTION: Molten Al alloy 99 is supplied into a die 21 from a melting furnace 9 by an automatic molten metal supplying means 91. The molten metal is directionally solidified by a casting means 2. A semi-product like work 1 having fine crystal grains is taken out in the semi-cooling state, and solution treatment is executed to the work 1 in a solution treatment furnace 3. The work 1 is rapidly cooled with water, etc., in a quenching means 4. A sprue part and the feeder head part, etc., 11 are cut off by a cutting means 98. The work 1 subjected to the cutting treatment of the spure, etc., is temper-anneald, etc., in an aging furnace 5. Shot blast treatment is then applied to the surface of the work 1 with a hot blasting means 6. The work 1 after shot blast is machined by a machining means 7. To the work 1 after machining, the check of air leakage, etc., is executed by an immersion air-tight checking means 8. Thus, the casting cycle time can be shortened.