To provide a catalytic converter and its manufacturing method for eliminating a press-in process of an assembly of a catalyst carrier and a mat to a cylindrical casing.

(1) This catalytic converter 1 has the assembly 10 of the catalyst carrier 11 and the mat 12 wound on the outer periphery, two surrounding bodies 20 having an almost semicircular cross section for sandwiching the assembly 10 and the cylindrical casing 30 for inserting the assembly 10 and the two surrounding bodies 20. A shaft directional end part 21 of the surrounding bodies 20 reduces in the radial direction. (2) The catalytic converter 1 is manufactured in such a way that the assembly 10 of winding the mat 12 on the outer periphery of the catalyst carrier 11 is sandwiched by the two surrounding bodies 20 having an almost semicircular cross section, and is compressed up to a prescribed dimension, and is inserted into the cylindrical casing 30 in a state of holding a compression state, and then, the compression state is released.