Provided is a fluid machine which can be produced to have an increased weld strength and an increased reliability, at a reduced production cost. A first and a second shells (78, 80), each having a rim and a sealing portion constituting part of the rim, are butted together with the rims (78a, 80a) held together to form a groove (82) and with the sealing portions (96, 98) in contact with each other, and joined together by a weld (84) formed in the groove over the entire length of the groove to be separated from the sealing portions by a space (100).