A refrigerator comprising: a plurality of wall modules (11, 12, 13, 14, 15, 16, 17) including a top wall module, a bottom wall module, a rear wall module, a left wall module, and a right wall module coupled together to define a storage chamber (21, 22, 23); and a cooling module configured to be detachably coupled to at least one of the rear wall module, the left wall module or the right wall module, the cooling module including a cooling module body defining a cold air producing space (53, 63), a compressor, a condenser, and an evaporator (54, 64) arranged in the cold air producing space (53, 63) to produce cold air, characterized in that at least one of the rear wall module, the left wall module, or the right wall module is a duct wall module coupled to the cooling module and including: an inner case (31, 131) defining the storage chamber (21, 22, 23) and having a supply hole (32, 42, 132) and a collecting hole (33, 43, 133); an outer case (36, 136) coupled to the inner case (31, 131); insulation (37, 137) provided between the inner case (31, 131) and the outer case (36, 136); a supply duct (38, 48, 138) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the supply hole (32, 42, 132) of the inner case (31, 131) to supply the cold air produced from the cooling module to the storage chamber (21, 22, 23); and a collecting duct (39, 49, 139) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the collecting hole (33, 43, 133) of the inner case (31, 131) to bring air from the storage chamber (21, 22, 23) back to the cooling module, wherein the supply duct (38, 48) and the collecting duct (39, 49) are buried in the insulation (37, 137). a plurality of wall modules (11, 12, 13, 14, 15, 16, 17) including a top wall module, a bottom wall module, a rear wall module, a left wall module, and a right wall module coupled together to define a storage chamber (21, 22, 23); and a cooling module configured to be detachably coupled to at least one of the rear wall module, the left wall module or the right wall module, the cooling module including a cooling module body defining a cold air producing space (53, 63), a compressor, a condenser, and an evaporator (54, 64) arranged in the cold air producing space (53, 63) to produce cold air, characterized in that at least one of the rear wall module, the left wall module, or the right wall module is a duct wall module coupled to the cooling module and including: an inner case (31, 131) defining the storage chamber (21, 22, 23) and having a supply hole (32, 42, 132) and a collecting hole (33, 43, 133); an outer case (36, 136) coupled to the inner case (31, 131); insulation (37, 137) provided between the inner case (31, 131) and the outer case (36, 136); a supply duct (38, 48, 138) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the supply hole (32, 42, 132) of the inner case (31, 131) to supply the cold air produced from the cooling module to the storage chamber (21, 22, 23); and a collecting duct (39, 49, 139) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the collecting hole (33, 43, 133) of the inner case (31, 131) to bring air from the storage chamber (21, 22, 23) back to the cooling module, wherein the supply duct (38, 48) and the collecting duct (39, 49) are buried in the insulation (37, 137). an inner case (31, 131) defining the storage chamber (21, 22, 23) and having a supply hole (32, 42, 132) and a collecting hole (33, 43, 133); an outer case (36, 136) coupled to the inner case (31, 131); insulation (37, 137) provided between the inner case (31, 131) and the outer case (36, 136); a supply duct (38, 48, 138) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the supply hole (32, 42, 132) of the inner case (31, 131) to supply the cold air produced from the cooling module to the storage chamber (21, 22, 23); and a collecting duct (39, 49, 139) arranged between the inner case (31, 131) and the outer case (36, 136) to be coupled to the collecting hole (33, 43, 133) of the inner case (31, 131) to bring air from the storage chamber (21, 22, 23) back to the cooling module, wherein the supply duct (38, 48) and the collecting duct (39, 49) are buried in the insulation (37, 137).