PURPOSE: To obtain continuously the reinforced glass fiber material capable of bending by heating and heat welding to each other by pulling a glass fiber bundle collected in the fiber direction in the bundle direction, passing the bundle successively through heat-melted sulfur and a molding machine, and hardening said bundle by cooling.

CONSTITUTION: A fiber bundle 2 is formed by collecting plural unit glass fiber bundles 2a obtained by collecting countless glass filaments in the fiber direction, or a cloth sheet 2b is formed out of the glass fiber bundle 2 obtained by arranging the unit glass fiber bundles 2a crosswise. These materials are pulled from a supply section 5 through pinch rolls 6 and 6 in the direction indicated by the arrow a. A sulfer heat-melting tank 7, a molding machine 4 and a cooler 8 are arranged on the pulling line. The pulled fiber roving 2 or the cloth sheet 2b are passed successively through the heat melting tank 7, the molding machine 4 and the cooler 8. The pulled glass fiber bundle 2 or the cloth sheet 2b are infiltrated with molten sulfur in the heat-melting tank 7 to the space between fibers 1 and 1.