Simultaneous measurements of ionic and electronic conductivities around the stoichiometric composition have been carried out on liquid Sn–Se, Sb–Se and Bi–Se alloys by applying the residual potential theory. The ionic conductivity, σi, in liquid Sn–Se and Sb–Se alloys increases with increasing temperature, while, in liquid Bi–Se alloys, it decreases with increasing temperature. The isothermal σi in liquid Sn–Se and Sb–Se alloys at higher temperatures exhibits a minimum at the stoichiometric composition of SnSe and Sb2Se3, respectively, and, on the other hand, it shows a maximum at Bi2Se3 in liquid Bi–Se alloys. Values of σi at SnSe, Sb2Se3 and Bi2Se3 near the melting temperature are 7.40 Sm−1 at 1173 K, 0.448 Sm−1 at 893 K and 45.3 Sm−1 at 993 K, respectively, which are about two orders of magnitude smaller than the corresponding electronic conductivities, σe. The value of σi of liquid Bi2Se3, which is the largest among three liquids, is roughly comparable to that for ionic liquid alloys such as Ag and Tl-chalcogenides. In contrast, liquid Sb2Se3 indicates the smallest σi due to the strong covalent bonding between unlike atoms. The minimum of the σi-isotherm at SnSe and Sb2Se3 in liquid Sn–Se and Sb–Se alloys also reflect the covalent nature in these liquids.