The present invention has as its problem the provision of a bulk oxide superconductor which has a high workability and high critical current density characteristic regardless of the external conditions and solves the problem by limiting the amount of addition of Ag to 5 mass % or less, using the QMG method to produce a bulk superconductor and thereby obtain a single crystal-like bulk superconductor of a structure with parts where Ag particles are present and parts where Ag particles are not present made to adjoin each other.