Disclosed herein is an apparatus for vulcanizing rubber, particularly for vulcanizing the ends of endless rubber belts. The apparatus disclosed herein is a lightweight and portable steam heated vulcanization apparatus which comprises upper and lower platens comprising hollow bodies having a rigid outer wall and a flexible inner wall and adapted to receive steam therein and transmit heat and pressure to a rubber belt placed between the flexible inner walls of the platens. A steam source is connected to the platens for delivery of steam and a plurality of connecting bolts pass through apertures in the platens and the belt material therebetween to align the platens and secure them together so as to apply pressure to the belt in combination with heat for optimal vulcanization.