The invention discloses a multi-spindle automatic tool changing device, and relates to the technical field of numerical-control machine tools. The multi-spindle automatic tool changing device comprises a base, an Y-axis worktable, an X-axis movement module, Z-axis spindle machining assemblies, a tool magazine and Z-axis positioning jigs. The Y-axis worktable is positioned on the base, the Z-axis positioning jigs include a Z1-axis positioning jig, a Z2-axis positioning jig and a Z3-axis positioning jig, and the Z1-axis positioning jig, the Z2-axis positioning jig and the Z3-axis positioning jig are arranged on the Y-axis worktable side by side along an X-axis direction; the X-axis movement module is arranged at the rear end of the base, the Z-axis spindle machining assemblies include a Z1 spindle machining assembly, a Z2 spindle machining assembly and a Z3 spindle machining assembly; the tool magazine is arranged below the X-axis movement module. The multi-spindle automatic tool changing device has the advantages that tools can be automatically changed, automatic control can be facilitated, the multi-spindle automatic tool changing device can bring convenience for workers during maintenance and repair, the labor intensity of the workers can be relieved to a great extent, and the production efficiency can be effectively improved.