A production process of a thick-film tape-shaped RE-type (123) superconductor having a high critical current value. The production process has the steps of providing a composite substrate having Gd2Zr2O7 and CeO2 stacked in that order onto a Hastelloy substrate, coating a raw material solution prepared by dissolving a trifluoroacetate of Y and Ba and a naphthenate of Cu onto the composite substrate, heat treating the coated composite substrate by calcination, then subjecting the calcined assembly to intermediate heat-treatment at a temperature below the temperature of heat-treatment for superconductor production, and then heat treating the assembly in an argon gas atmosphere under conditions of highest heating temperature 760° C., water vapor partial pressure 13.5%, and oxygen partial pressure 0.09% for superconductor production to produce a tape-shaped RE-type (123) superconductor having a YBCO superconducting film having a thickness of more than about 2 μm.