To reduce the phase transition temperature at which an LMO crystal lattice, which constitutes the oxide layer serving as an interlayer or as a part of an interlayer, is a cubic crystal, the present invention provides a base material for a superconductor wire material comprising an oxide layer (LMO layer (22)) primarily having a crystalline material represented by the compositional formula Laz(Mn1-xMx)wO3+ delta (where M is at least one element selected from Cr, Al, Co, and Ti; delta is the oxygen nonstoichiometry; 0 < w/z < 2; and 0 < x <= 1).