To provide a sandwich structure plate having higher rigidity strength than a zeta-core sandwich structure plate which has a flow passage formed in the interior though.

This sandwich structure plate has a core material 1 of the shape of MIURA folding and two sheets of metal plates 2 joined by seam welding respectively to chevron fold parts on both sides of the core material 1. Different from a zeta-core, the core material 1 has no summit surface, so the rate of effective part as a core material gains so mush, and rigidity strength gets higher than a zeta-core sandwich structure plate even though a flow passage in the interior is formed. This sandwich structure plate is continuously mass produced through a core material forming process in which a metallic flat plate is formed into a core material 1 in the shape of MIURA folding and a joining process in which two sheets of metal plates 2 are seam welded in a zigzag form on both sides of chevron fold parts of the core material 1.