A linear compressor comprising: a shell to which a suction pipe is coupled; a cylinder disposed inside the shell to define a compression space (P); a piston reciprocating inside the cylinder to compress a refrigerant in the compression space (P); and a muffler coupled to the piston and having an inlet through which the refrigerant is introduced and an outlet through which the refrigerant is discharged, wherein the muffler includes a plurality of flow tubes extending in a flow direction of the refrigerant from the inlet to the outlet, wherein the plurality of flow tubes include at least one variable portion having a flow cross-sectional area widened in the flow direction, wherein the at least one variable portion is formed in any one of the plurality of flow tubes , wherein the muffler includes: a first muffler , at least a part of which is disposed inside the piston ; a second muffler coupled to a rear portion of the first muffler ; and a third muffler in which the second muffler is accommodated and which is coupled to a rear portion of the piston , wherein the plurality of flow tubes includes a first flow tube provided in the first muffler and a second flow tube provided in the second muffler , wherein the at least one variable portion is formed in the first flow tube , and wherein cross sections of outlets of the first flow tube are larger than cross sections of inlets of the first flow tube , characterized in that : an outer side and an inner side of the first flow tube have an inclined structure extending continuously from the inlet to the outlet. a shell to which a suction pipe is coupled; a cylinder disposed inside the shell to define a compression space (P); a piston reciprocating inside the cylinder to compress a refrigerant in the compression space (P); and a muffler coupled to the piston and having an inlet through which the refrigerant is introduced and an outlet through which the refrigerant is discharged, wherein the muffler includes a plurality of flow tubes extending in a flow direction of the refrigerant from the inlet to the outlet, wherein the plurality of flow tubes include at least one variable portion having a flow cross-sectional area widened in the flow direction, wherein the at least one variable portion is formed in any one of the plurality of flow tubes , wherein the muffler includes: a first muffler , at least a part of which is disposed inside the piston ; a second muffler coupled to a rear portion of the first muffler ; and a third muffler in which the second muffler is accommodated and which is coupled to a rear portion of the piston , wherein the plurality of flow tubes includes a first flow tube provided in the first muffler and a second flow tube provided in the second muffler , wherein the at least one variable portion is formed in the first flow tube , and wherein cross sections of outlets of the first flow tube are larger than cross sections of inlets of the first flow tube , characterized in that : an outer side and an inner side of the first flow tube have an inclined structure extending continuously from the inlet to the outlet. a first muffler , at least a part of which is disposed inside the piston ; a second muffler coupled to a rear portion of the first muffler ; and a third muffler in which the second muffler is accommodated and which is coupled to a rear portion of the piston , wherein the plurality of flow tubes includes a first flow tube provided in the first muffler and a second flow tube provided in the second muffler , wherein the at least one variable portion is formed in the first flow tube , and wherein cross sections of outlets of the first flow tube are larger than cross sections of inlets of the first flow tube , characterized in that : an outer side and an inner side of the first flow tube have an inclined structure extending continuously from the inlet to the outlet. <EOS>