PURPOSE: To change a lighting load in the desired dimmed condition with time passing through and store the dimmed condition to be desired by providing means for storing a dimming command signal in a memory gradually in time and a means for reading out it gradually in time.

CONSTITUTION: A dimming command signal having a level such as a voltage corresponding to a dimmed condition is stored in a memory 9 gradually in time by sampling it at the first time interval to be predtermined. Consequently, a desired dimmed condition can be stored in the memory 9. And a storing work into the memory 9 can be performed in a short time by setting the first time internal in short. A stored content in the memory 9 is read out at the second time internal to be predtermined gradually in time, and a luminous load is controlled to dim based on the stored content. The dimmed condition can be thus chanted at the second time interval to be desired.