a method of producing nb 3 sn superconducting wire , including the steps of : preparing a plurality of sn modules obtained by burying sn - based metal cores in a cu - based metal matrix and a plurality of nb modules obtained by burying nb - based metal filaments in a cu - based metal matrix ; bundling the nb modules and the sn modules such that the nb modules surround the sn modules and obtaining an assembly ; inserting the assembly in a tubular member of cu - based metal which internally comprises tube - like shaped ta - based metal or nb - based metal which serves as a diffusion barrier and obtaining a composite ; drawing the composite ; and heat - treating the composite .