A nontoxic high-Tc (=118 K) superconductor CuBa2Ca3Cu4O12-y (Cu-1234)
has a low superconducting anisotropy (gamma = 1.5) and a long coherenc
e length along c-axis (xi(c) = 10 Angstrom). The superconducting aniso
tropy of Cu-1234 was compared with other cuprate superconductors by us
ing the experimental data from a common measurement method of anisotro
py. The Cu-1234 was found to have the least superconducting anisotropy
among cuprate superconductors. The least anisotropy originates from a
strong superconducting-coupling between superconducting Ca3Cu4O8-bloc
k layers mediated by superconductive charge-reservoir CuBa2O4-y layer,
the thickness of the superconducting block layer (9.6 Angstrom) and h
igh carrier concentration.