Abstract: To provide a sheet formed product that, in addition to being thin, has a small groove interval, groove width, and groove depth, that has a large contact surface area with oxygen gas or hydrogen gas, that is suitable for simply and at low cost producing a lightweight compact separator, and a manufacturing method for same. In the sheet formed product (amorphous thin sheet) according to the present invention, a metal matrix on which is formed a passivation layer on a surface layer thereof and that exhibits corrosion resistance has a three-dimensional surface structure, for example a groove-like uneven shape on a surface thereof. On the front surface having the uneven shape (or also on the back surface), particles of a conductive material component penetrate the passivation layer, and are exposed on the surface without being in solid solution in the metal matrix.