PURPOSE: To enable to transfer heat cheaply and with high performance from a solar heat collector to a heat accumulator without using any auxiliary power by a method wherein the heat accumulator is located lower than the solar heat collector and at the same time mixed refrigerant is used.

CONSTITUTION: The solar heat collecting device is equipped with the solar heat collector 1, the heat accumulator 3 located lower than the solar heat collector 1, a gas-liquid separator 2 located higher than the solar heat collector 1 and a heat exchanger 4 arranged within the heat accumulator 3. The low position side of said gas-liquid separator 2 is connected through the heat exchanger 4 to the low position side of the solar heat collector 1 by means of a piping. The outlet of a piping connected to the high position side of the gas-liquid separator 2 is arranged at the inlet side of the heat exchanger 4. The mixed heat transfer medium comprising in mixing refrigerant having low boiling point with solvent having high boiling point is used as heat transfer medium.