A seal structure includes a seal body. The seal body is sandwiched between a case and a cover and provided between a space and fastening regions. The space is formed by the case and the cover. The case and the cover is fastened at the fastening regions to compress the seal body in a compression direction. The seal body includes first regions and second regions. The first regions correspond to the fastening regions. Each of the second regions is provided between one of the first regions and another of the first regions. Reaction force in the compression direction in the seal body located at the first regions is smaller than reaction force in the compression direction in the seal body located in the second regions.