PURPOSE: To efficiently and safely recover a thinner from a thinner-containing waste fluid such as a paint waste fluid by utilizing solar heat.

CONSTITUTION: A thinner-containing waste fluid is mixed with water to be infiltrated in an absorbing material to prepare a raw material C which is, in turn, introduced into a distillation chamber 3 to be set toward the sun. The upper surface plate 4 of the distillation chamber 3 is transparent sand the outer surface thereof is cooled by water. Steam and thinner vapor are condensed on the rear surface of the upper surface plate 4. The condensate flows down by the inclination of the upper surface plate 4 to be gathered to a gathering trough 8 to be sent to a recovery container 10.