A disposing method for an inlet pipe in a muffler that includes an outer shell, an inlet pipe, and a separating plate, the disposing method comprising: a first step of inserting the inlet pipe into the outer shell from an opening at one end of the outer shell; a second step of disposing the inlet pipe by moving the inlet pipe within the outer shell in a direction substantially orthogonal to the direction of insertion of the inlet pipe; and a third step of disposing the separating plate by inserting the separating plate into the outer shell from the opening at the other end of the outer shell.