A tooth cleaning device having an internal fluid conduit, the tooth cleaning device comprising: a main body, a tube being provided in said main body and selectively connectable with a drive unit; and a cleaning body which is to be assembled to one side of the main body, and has the internal fluid conduit formed in the cleaning body and connectable with the tube, wherein at least one nozzle is formed to be opened at one end of the internal fluid conduit, wherein when the main body and the cleaning body are assembled, one end of the tube is connected to one end of the internal fluid conduit and defines a continuous flow path, wherein a flange is separably coupled to an upper portion of the main body, wherein a coupling protrusion and a coupling channel, which correspond to each other, are formed on the cleaning body and the flange, respectively, and during a process in which the cleaning body is coupled to the flange, the coupling protrusion is guided along the coupling channel and then caught and fixed by one side of the coupling channel, wherein the coupling channel is formed in an inner surface of the flange, wherein a tube guide is provided below the flange, the tube guide includes a guide plate which is supported and fixed on an inner surface of the main body, a tube coupling portion which protrudes from a bottom surface of the guide plate and is coupled to one end of the tube, and a conduit insertion portion which protrudes from an upper surface of the guide plate and is positioned in the flange, and when the cleaning body is coupled to the flange, at least a part of the conduit insertion portion is inserted into the internal fluid conduit of the cleaning body. a main body, a tube being provided in said main body and selectively connectable with a drive unit; and a cleaning body which is to be assembled to one side of the main body, and has the internal fluid conduit formed in the cleaning body and connectable with the tube, wherein at least one nozzle is formed to be opened at one end of the internal fluid conduit, wherein when the main body and the cleaning body are assembled, one end of the tube is connected to one end of the internal fluid conduit and defines a continuous flow path, wherein a flange is separably coupled to an upper portion of the main body, wherein a coupling protrusion and a coupling channel, which correspond to each other, are formed on the cleaning body and the flange, respectively, and during a process in which the cleaning body is coupled to the flange, the coupling protrusion is guided along the coupling channel and then caught and fixed by one side of the coupling channel, wherein the coupling channel is formed in an inner surface of the flange, wherein a tube guide is provided below the flange, the tube guide includes a guide plate which is supported and fixed on an inner surface of the main body, a tube coupling portion which protrudes from a bottom surface of the guide plate and is coupled to one end of the tube, and a conduit insertion portion which protrudes from an upper surface of the guide plate and is positioned in the flange, and when the cleaning body is coupled to the flange, at least a part of the conduit insertion portion is inserted into the internal fluid conduit of the cleaning body.