A reactor (6) for pyrolysing waste, in particular rubber tires, said reactor comprising a pyrolysis space (68), an inlet port (63) and an outlet port (64) enabling a flow across the pyrolysis space (68) of a heating medium for transferring heat required for the pyrolysis, and a lower discharge port (62) for discharging solid residues of the pyrolysis. The invention is, characterized in that—it comprises a baffle means (65) made of a plate material and enabling a gravitational slipping of the solid residues towards the discharge port (62), which baffle means (65) has openings (66) allowing the flow of the heating medium and is arranged to divide the inner space of the reactor (6) to form an upper pyrolysis space (68) and a lower space and—one of the inlet and outlet ports (63, 64) is in connection with the pyrolysis space (68) and the other one with the lower space. The invention is also an apparatus comprising the above reactor (6).