PURPOSE: To enable to receive solar rays efficiently, by providing a driving mechanism which includes solar-ray sensors for detecting solar rays and turns a reflector plate directly through utilization of the difference of change in the volume of a heating medium corresponding to the quantity of solar rays received by the solar-ray sensors.

CONSTITUTION: A heat collecting pipe 7 is disposed at the focal point of a reflector plate 4, and two solar-ray sensors 12, 13 charged with a heating medium which causes change in volume by solar heated absorbed thereby are disposed at one side of holding portions 5, 6 of the reflector plate 4. Further, cylindrs 16, 17 having respectively pistons 14, 15 fitted therein in a freely movable manner are provided in the solar-ray sensors 12, 13, and the two pistons 14, 15 are interconnected by a chain 18 so that the holding portion 5, 6 can be driven by the chain 18. In case that solar rays is radiated, for instance, slantwise to the reflector plate 4 as shown in the drawing, thermal expansion of coolant is greater on the side of sensor 12 than on the side of sensor 13, so that the piston 14 associated with the sensor 12 is pushed upward. Here, since the piston 14 is interconnected to the piston 15 by the chain 18, the piston 15 is pushed downward relatively and turns the holding portion 5. Resultantly, the reflector plate 4 can be turned toward the solar rays.