Superconducting　nanowires　underpin　the　development　of　a　variety　of　highly　advanced　quantum　devices　such　as　single-photon　detectors　and　quantum　circuits.　In　1D　superconducting　nanowires,　topological　fluctuations　of　the　superconducting　order　parameter,　known　as　phase　slips,　severely　influence　the　electrical　transport.　In　3D　systems,　however,　phase-slip　events　are　generally　considered　to　be　insignificant.　Here,　details　on　the　observation　of　a　reentrant　resistive　state　in　3D　superconducting　diamond　nanowires　(DNWs)　are　reported.　This　exotic　resistive　state　alters　the　trend　of　the　superconducting　transition　with　an　abrupt　change　of　the　temperature　and　magnetic-field　coefficients　of　resistivity　and　the　current　coefficient　of　voltage.　This　reentrant　resistive　state　is　interpreted　as　being　a　result　of　quantum　phase　slips　in　the　bamboo-like　DNWs　consisting　of　multiple　sequential　grain-boundary-grain　junctions.　The　results　provide　the　first　evidence　that　quantum　phase　slips　can　also　play　a　crucial　role　in　determining　the　electrical　transport　properties　of　3D　superconducting　nanowires.