A muffler for an air-conditioning apparatus , comprising: a muffler main body , having a tubular shape, in which an inlet small diameter portion is connected to a large diameter portion through an enlarged diameter portion , and the large diameter portion is connected to an outlet small diameter portion through a reduced diameter portion ; an inlet pipe connected to the inlet small diameter portion of the muffler main body ; and an outlet pipe connected to the outlet small diameter portion of the muffler main body , the inlet pipe having an inserted pipe portion disposed in the muffler main body , the inserted pipe portion being inserted into the muffler main body from the inlet small diameter portion and extending from a starting point of the enlarged diameter portion to an inside of the muffler main body , the inserted pipe portion having an upper inserted pipe portion positioned on an inlet side of the muffler main body and a lower inserted pipe portion positioned on an outlet side of the muffler main body , wherein the upper inserted pipe portion has an inner diameter equal to an inner diameter of the inlet pipe on an upstream part of the inlet small diameter portion , and wherein the lower inserted pipe portion has a distal end positioned at a center of a length from an inlet to an outlet of the muffler main body , characterized in that the lower inserted pipe portion has an inner diameter smaller than an inner diameter of the upper inserted pipe portion , wherein a ratio of an inner diameter D of the muffler main body to an inner diameter D 2 of the lower inserted pipe portion is set to satisfy D/D 2 >5.7, and wherein, when a length of the upper inserted pipe portion is defined as L 2 , and a length of the lower inserted pipe portion is defined as L 3 , a ratio of L 3 to L 2 is set to satisfy 1.5<L 3 /L 2 <3. a muffler main body , having a tubular shape, in which an inlet small diameter portion is connected to a large diameter portion through an enlarged diameter portion , and the large diameter portion is connected to an outlet small diameter portion through a reduced diameter portion ; an inlet pipe connected to the inlet small diameter portion of the muffler main body ; and an outlet pipe connected to the outlet small diameter portion of the muffler main body , the inlet pipe having an inserted pipe portion disposed in the muffler main body , the inserted pipe portion being inserted into the muffler main body from the inlet small diameter portion and extending from a starting point of the enlarged diameter portion to an inside of the muffler main body , the inserted pipe portion having an upper inserted pipe portion positioned on an inlet side of the muffler main body and a lower inserted pipe portion positioned on an outlet side of the muffler main body , wherein the upper inserted pipe portion has an inner diameter equal to an inner diameter of the inlet pipe on an upstream part of the inlet small diameter portion , and wherein the lower inserted pipe portion has a distal end positioned at a center of a length from an inlet to an outlet of the muffler main body , characterized in that the lower inserted pipe portion has an inner diameter smaller than an inner diameter of the upper inserted pipe portion , wherein a ratio of an inner diameter D of the muffler main body to an inner diameter D 2 of the lower inserted pipe portion is set to satisfy D/D 2 >5.7, and wherein, when a length of the upper inserted pipe portion is defined as L 2 , and a length of the lower inserted pipe portion is defined as L 3 , a ratio of L 3 to L 2 is set to satisfy 1.5<L 3 /L 2 <3. <EOS>