A dishwasher comprising: a tub having a washing space therein and comprising a bottom, an upper wall, one sidewall, the other sidewall, and a rear wall; a door, disposed at a front side of the tub, configured to open or close the washing space; and a drying device configured to dry the washing space, wherein the bottom and the upper wall face each other in a vertical direction, the rear wall and the door face each other in a first direction, one sidewall and the other sidewall face each other in a second direction, an inlet port is formed in a rear upper portion of one sidewall of the tub, and an outlet port is formed in one rear side portion of the bottom of the tub, wherein the drying device comprises: a drying duct configured to communicate with the inlet port and the outlet port, disposed outside the tub, and comprising a condensing duct and a return duct; a fan configured to allow air in the drying duct to flow; and a heater configured to heat the air in the drying duct, wherein the condensing duct comprises: a first condensing duct facing an outer surface of the one sidewall and having an upstream end adapted to communicate with the inlet port; and a second condensing duct disposed lower than the bottom and having an upstream end adapted to communicate with a downstream end of the first condensing duct, and wherein an upstream end of the return duct is adapted to communicate with a downstream end of the second condensing duct, and a downstream end of the return duct is adapted to communicate with the outlet port, characterized in that a second water drain port through which a water is discharged from an inside of the second condensing duct to an outside is formed at a bottom of the second condensing duct. a tub having a washing space therein and comprising a bottom, an upper wall, one sidewall, the other sidewall, and a rear wall; a door, disposed at a front side of the tub, configured to open or close the washing space; and a drying device configured to dry the washing space, wherein the bottom and the upper wall face each other in a vertical direction, the rear wall and the door face each other in a first direction, one sidewall and the other sidewall face each other in a second direction, an inlet port is formed in a rear upper portion of one sidewall of the tub, and an outlet port is formed in one rear side portion of the bottom of the tub, wherein the drying device comprises: a drying duct configured to communicate with the inlet port and the outlet port, disposed outside the tub, and comprising a condensing duct and a return duct; a fan configured to allow air in the drying duct to flow; and a heater configured to heat the air in the drying duct, a drying duct configured to communicate with the inlet port and the outlet port, disposed outside the tub, and comprising a condensing duct and a return duct; a fan configured to allow air in the drying duct to flow; and a heater configured to heat the air in the drying duct, wherein the condensing duct comprises: a first condensing duct facing an outer surface of the one sidewall and having an upstream end adapted to communicate with the inlet port; and a second condensing duct disposed lower than the bottom and having an upstream end adapted to communicate with a downstream end of the first condensing duct, and a first condensing duct facing an outer surface of the one sidewall and having an upstream end adapted to communicate with the inlet port; and a second condensing duct disposed lower than the bottom and having an upstream end adapted to communicate with a downstream end of the first condensing duct, and wherein an upstream end of the return duct is adapted to communicate with a downstream end of the second condensing duct, and a downstream end of the return duct is adapted to communicate with the outlet port, characterized in that a second water drain port through which a water is discharged from an inside of the second condensing duct to an outside is formed at a bottom of the second condensing duct.