An exhaust manifold A includes, in its collecting part structure, a plurality of branch pipes 2 to 5 that are connected with a flange head 1, a collecting part 6 that collects and contains exhaust-gas downstream side end portions 2a to 5a of the branch pipes 2 to 5, a partition plate 10 that is arranged in a state where its exhaust-gas downstream side end portion 10a projects in the interior of the collecting part 6, and a sensor attachment boss part 9 that is fixed by weld line X on a part of an outer circumferential portion of the collecting part 6 in a state where it faxes an insertion hole 6f formed in the collecting part 6. Insertion holes 6g and 6h are formed in a reduced diameter portion 6e of the collecting part 6 of the exhaust manifold A, and the partition plate 10 is fixed by a weld line X5 with a portion of the outer circumferential portion of the collecting part 6 in a state where portions 10c and 10d of both end portion of the partition plate 10 are inserted in and positioned to the insertion holes 6g and 6h.