An oil reconversion devices 1a and 1b for waste plastics which thermally crack a waste plastic Ro by heating it and converts a generated cracker gas Gr into oil by cooling it, equipped with a thermal cracking bath 2 which has a bath main body 4 placed inside a coil 3 . . . , induction-heats the bath main body 4 by feeding a high-frequency current through the coil 3 . . . , and thermally cracks at least a molten plastic Rd obtained from the waste plastic Ro to generate the cracker gas Gr, an injection port 5 through which the waste plastic Ro is injected, a feeder 6 which supplies the waste plastic Ro injected through this injection port 5 to the thermal cracking bath 2 via a forced or direct feeding means Ua or Ub without a bath, and an oil conversion processor 7 which cools and converts the cracker gas Gr generated by the thermal cracking bath 2 into oil.