A full mask sheet, a mask sheet assembly and an evaporation device are provided. The full mask sheet includes a sheet body including a first surface which is configured to support multiple fine metal mask sheets of the mask sheet assembly, and the sheet body is provided with multiple openings which are configured to expose mask pattern regions of the fine metal mask sheets. The sheet body includes a first region near a circumferential edge and a second region surrounded by the first region, and a first surface of the second region protrudes from a first surface of the first region in a direction perpendicular to the sheet body. The first surface of the first region is provided with a support portion which avoids the opening, and the support portion is configured to support the multiple fine metal mask sheets together with the first surface of the second region.