PURPOSE: To dry distillate oil shale in a high oil yield and at a high overall thermal efficiency, by supplying a solid heat medium and a gaseous heat medium to a fluidizing bed atmosphere.

CONSTITUTION: Oil shale crushed into a particle size ≤10mm is continuously supplied at a constant rate to a fluidizing bed dry distillation furnace 1 and, at the same time, a solid heat medium is sent via a line 18 from a furnace 2 and a gaseous heat medium via line 25 each to the furnace 1 to fluidize and dry distill the oil shale by direct heating. The gaseous material is introduced into a separation column 3, cooled therein and withdrawn as a product distillate. A part of the combustible gas contg. inert gas is introduced via a line 15 into a heat exchanger 4. The dry distillation residue is sent to a furnace 2, where it is burned with air supplied via a line 8 and the obtd. hot shale is partially sent to the heat exchanger 4 to preheat the combustible gas. The exhaust gas from the furnace 2 is sent to a heat exchanger 5 and subjected to heat exchange with water supplied via line 21 to generate steam, which is introduced into the heat exchanger 4 to generate supperheated steam. This steam is supplied together with the combustible gas from a line 15 and process air from a line 19, to the furnace 1.