Inner structured and bonded ( ISB) panel, a type of metallic sandwich panel, consists of two thin skin plates bonded to a micropatterned inner structure. It has an overall thickness of 1-3 mm and attractive properties, such as ultralight weight, high efficiency in stiffness to weight and strength to weight ratios. In this paper, a new joining process using resistance welding is developed for joining ISB panels. Electrodes with curved surface are applied to join the two skin plates and micropatterned inner structure, while two stoppers are used to keep a gap between the electrodes during welding. Owing to this gap, the inner structure shape is maintained without damage. Current, welding time and electrode gap were selected as the process parameters. This process is simpler and more suitable for mass production than previous processes for joining the panel. Appropriate welding conditions were studied by measuring the tensile load with respect to variations in welding time and electrode gap.