This　paper　aims　to　develop　a　novel　tungsten　inner　gas　(TIG)　welding　torch　in　order　to　join　thin　sheets　efficiently.　Using　a　narrowing　nozzle　(constricted　nozzle)　inside　a　conventional　TIG　torch　can　critically　improve　the　position　accuracy　of　the　tungsten　electrode　and　also　the　arc　plasma　characteristics　and　heat　input　density.　In　order　to　evaluate　the　efficiency　of　this　new　torch,　weld　bead　appearance　and　cross-section　images　were　examined　by　an　optical　microscope,　scanning　electron　microscope　(SEM),　and　electron　back　scatter　diffraction　patterns　(EBSD).　The　results　showed　that　in　all　cases,　the　weld　bead　profile　was　stable　without　undercut　and　burn-through.　Full　penetration　weld　was　seen.　The　width　of　weld　bead　on　the　bottom　surface　was　increased　much　in　comparison　to　conventional　TIG　welding.　However,　the　results　from　SEM　and　EBSD　images　indicated　that　in　the　case　of　low　welding　current,　the　blowholes　were　found　out　on　the　side　of　the　thinner　material　(SS400).　The　penetration　of　SUS430　material　to　SS400　material　was　not　good.　It　seems　that　no　fusion　of　SUS430　material　to　SS400　at　the　bottom　surface　can　be　seen.　Meanwhile,　no　blowholes　were　seen　in　the　case　of　high　welding　current.　The　penetration　was　better,　and　the　fusion　was　reached　on　the　bottom　surface.