PURPOSE: To constitute the title sheet so that gaps are not generated between parallel fibers, by a method wherein long fibers arranged in parallel with one another to form a sheet are connected with one another by making use of a heat-fusing sheet provided with a form of nonwoven fabric or braided fabric which is extremely thin and is loose.

CONSTITUTION: When a fiber sheet 1 where heat-fusing sheet 2,2 are caused to run respectively along both the front and rear is forced to pass through between a pair of hot press rollers 8, 8 the hot-melt heat-fusing sheets 2 are pressed against both the surfaces and the heat-fusing sheet 2 is cooled and solidified swiftly after passing through between the hot press rollers 8, 8. Therefore, a large number of long fibers 1a constituting the fiber sheet 1 become a state where they are connected with one another by the heat-fusing sheet 2 in a state of nonwoven fabric, a form of the sheet is set, a desired fibrous matter reinforcing sheet A is completed and wound up round a wind-up shaft 9 of a product. With this construction, it becomes that gaps are not generated among the fibers drawn up in a line. A lump of an adhesive agent stucks to a lateral fiber along the lateral fiber lies scattered concentratively locally within a fiber-reinforced plastic molded product and also lowering of strength of the whole of the product is eliminated.