In apparatus for vapor phase growing N or P type semiconductor layers on semiconductor substrates supported by a rotary support disposed in a reaction furnace, and various types of gases are admitted into the furnace through a pipe line network and valves, there is provided a control device for ON-OFF controlling the valves according to a predetermined program. The control device comprises a memory region for storing a process program group including a group of process programs including informations regarding a time for designating a process of vapor phase growth in the reaction furnace, gases utilized, flow quantity thereof and furnace temperature, and a system program that decodes the program group for producing control signals for the valves.