PURPOSE: To prevent generation of voids in the outer layer and an inner layer after molding of a laminated sheet, by a method wherein rolls are brought into contact with both sides of a resin-impregnated base material by providing a plurality of rolls on a position excluding a gateway part out of the whole length of a drying process where the resin-impregnated base material flows.

CONSTITUTION: Smoothness of both sides of a prepreg are improved by bringing both the sides of the prepreg into contact with several rolls during a drying process of the prepreg. Glass cloth 6 enters into a drying tower 7 after immersion in varnish 5 and passes through gaps among two sets of a top and bottom rolls 1, 3 and 2, 4. Each of the rolls 1, 2, 3, 4 is synchronized with the glass cloth and the glass cloth is compressed appropriately in each of the gaps among rolls 1, 3 and 2, 4. Each of the roll positions is obtained by excluding one fifth of the while length of the drying process from a gateway of the drying process.