PURPOSE: To heat continuously billets so as to match the production pitches of a continuous casting installation and a rolling side by segmenting the overall length of stationary beams by pitches, adjusting specifically the stroke of movable beams and detecting the occupying condition of the billets.

CONSTITUTION: The pitch segments P segmenting virtually the overall length of stationary beams 2 are respectively numbered and stored. Detectors 3, 10 are provided at the top end of a movable beam 5 on an ejection side and the point where a billet rides on the beam 5. Flags 1, 0 for indicating the presence and absence of the billet are set at every segment P into a stored tracking memory 11. The billet S1 is ejected by the advance as well as vertical movement of the beam 5 and the memory part thereof goes to 0. The beam 5 is moved upward in succession and when the detector 3 is turned on by the billet S2, the beam is stopped and lowered. The extent l1 of the movement of the billet S1 in this stage is measured with a stroke detector 13 and the (l1/P segment + the inter-billet spacing segment) is indexed, by which each flag of the memory 11 is updated. The billet S1' is then transferred to the working range of the beam 5 by a movable beam 4 on a feed side to turn on the detector 10, by which the presence of the extent of the movement of integer times the P with respect to the width of the billet S1' is confirmed. The extent l2 of the movement thereof is determined as the rate of stroke.