An exhaust gas purifying device includes a cylindrical shell, a flow channel pipe, and a lid member. The pipe is connected to the shell along a radial direction of the shell. The shell is a member that is formed in a cylindrical shape having a pair of open ends, and in which exhaust gases flow. The shell has at least one shell-side fitting groove that is formed at one of the ends, and in which the pipe is fittable. The lid member is a member that closes the one of the pair of ends of the shell, and has at least one lid-side fitting groove that is formed at a position facing the at least one shell-side fitting groove, and in which the pipe is fittable. The at least one shell-side fitting groove and the at least one lid-side fitting groove fit the pipe therein by holding the pipe therebetween.