PURPOSE: To uniformly heat or cool a material of angular cross section while conveying it, by providing fixed and movable beams with plural protrusion having prescribed shapes and located at equal intervals and by operating the movable beams to move the material of angular cross section while rotating it forward or backward.

CONSTITUTION: A conveyor, which is constructed at a hot billet cooling bed or the like, comprises plural fixed beams 1 and plural movable beams 2 laid in parallel with each other. The movable beams 2 are rotated forward or backward as shown by a chain-line locus 25. Each fixed beam 1 has protrusions 6 at prescribed intervals. Each protrusion 6 has a slope 7 extending upward in the direction of conveyance and having an inclination angle α of 45° or less and has an arc-shaped slope 9 extending downward in the direction of conveyance and having an inclination angle of 45° or more. Each movable beam 2 has protrusions 16 at the same intervals as those 6 of the fixed beam 1. Each protrusion 16 has a partially circular cross section. The movable beam 2 can be rotated forward and backward alternately to cause a material 3 to stay.