To obtain an electrically insulated laminate base paper having excellent resistance to silver ion migration and useful for printed wiring boards by adding highly acid-resistant synthetic hydrotalcite and without impairing the processability such as varnish impregnability and properties of a laminated sheet, particularly heat resistance.

This paper is obtained by adding to a pulp stock a highly acid- resistant synthetic hydrotalcite such as Mg4Al2(OH)12CO3.3H2O that can maintain the insoluble state for ≥20s in a 1mol/L HBr solution in an amount of 0.5 to 5wt.% (based on the absolute oven-dry weight of the electrically insulated laminate base paper).