PURPOSE: To obtain prepreg for a laminated sheet, which fas favorable coating and infiltrating properties, few bubbles and easy moldability, by a method wherein a depth of infiltration or immersion of resin varnish is made less than a thickness of a sheetlike base as the primary infiltration and a time up to the secondary infiltration from after the primary infiltration is specified.

CONSTITUTION: One side infiltration is adopted ordinarily as the primary infiltrating method and varnish is infiltrated or immersed into a base up to the middle of a thickness direction of the base. When the secondary infiltration is performed after the lapse of at least 5 seconds after completion of the primary infiltration, preferably after the lapse of at least 10 seconds, meanwhile resin varnish is infiltrated into up to details, a part where the resin varnish is not infiltrated is in existence by inclining toward one side of the base and at the time of the secondary infiltration deaeration of remaining air becomes easy. With this construction, prepreg having favorable infiltration properties through which a laminated sheet where generation of ply separation and measling etc. are few in a heat treatment process such as a solder reflow after moisture absorption treatment and it is superior in electric properties also can be obtained can be manufactured.