A method for manufacturing an Fe-Ni alloy cold-rolled sheet excellent in cleanliness and etching pierceability, comprising: preparing an Fe-Ni molten alloy, containing 30 to 45 wt. % nickel, and subjected to dephosphorization and decarburization; adding aluminum and flux to the Fe-Ni molten alloy in a ladle made of an MgO-CaO refractory containing 20 to 45 wt. %; strongly stirring the Fe-Ni molten alloy which contains the added aluminum and flux in the ladle to produce a CaO-Al.sub.2 O.sub.3 -MgO slag so as to react the Fe-Ni molten alloy with the CaO-Al.sub.2 O.sub.3 -MgO slag to deoxidize the Fe-Ni molten alloy while controlling a value of activity of SiO.sub.2 from 0.001 to 0.005 and a value of activity of Al.sub.2 O.sub.3 from 0.1 to 0.3 in the CaO-Al.sub.2 O.sub.3 -MgO slag, and the CaO-Al.sub.2 O.sub.3 -MgO slag having the following chemical composition: CaO and Al.sub.2 O.sub.3 : at least 57 wt. %, wherein the ratio of CaO/(CaO+Al.sub.2 O.sub.3) being at least 0.45, MgO: up to 25 wt. %, SiO.sub.2 : up to 15 wt. %, and oxides of metals having an oxygen affinity lower than that of silicon: up to 3 wt. % in total; casting the deoxidized Fe-Ni molten alloy into an ingot; and blooming, hot-rolling and cold-rolling the ingot to manufacture an Fe-Ni alloy cold-rolled sheet containing non-metallic inclusions comprising a composition in a region of a melting point of at least 1,600.degree. C., which region is defined by a liquidus curve of 1,600.degree. C. in a CaO-Al.sub.2 O.sub.3 -MgO ternary phase diagram and having a particle size up to 6 .mu.m in a total amount of up to 0.002 wt. % as converted into oxygen.