Abstract: An acidic tinplating electrolyte containing at least one sulfate selected from the sulfates of alkaline metals, ammonium, aluminum, manganese or chromium and an ethoxylated .alpha.-naphthol sulfonic acid in a known stannous sulfate or stannous phenolsulfonate electrolyte.This acidic tinplating electrolyte is suitable as a preplating electrolyte for a tinplate in which excellent corrosion resistance is required and also as an electrolyte for the production of a steel sheet having an extremely thin tin layer or an extremely thin iron-tin alloy layer, as a very dense and uniform tin layer is formed on the steel sheet by using the electrolyte of this invention.