PURPOSE: To control automatic opening/closing of curtain appropriately by allowing load control depending on the quantity of solar beam incident on a room and ambient temperature.

CONSTITUTION: A heat receiving plate 1 irradiated with solar beam, a first temperature detecting element 2 for detecting temperature of the heat receiving plate 1, and a second temperature detecting element 3 for detecting ambient temperature are contained in a case 9. A control circuit 7 controls a load 8 according to the relationship of temperatures detected through the first and second temperature detecting elements 2, 3. Eaves 4 for limiting quantity of solar beam incident on the heat receiving plate 1 depending on the elevation of the sun is protruding from above the heat receiving plate 1.