A treatment device for sterilizing, purifying, and/or deodorizing a fluid, comprising: a pipe comprising an inlet and an outlet and comprising an internal space through which a fluid moves; and a light source part disposed in the internal space and providing a light in the ultraviolet wavelength band to the fluid, the light source part comprising at least one light source unit comprising a substrate extending along a predetermined direction and a plurality of light sources disposed on the substrate along the predetermined direction, the light sources being light emitting diodes and emitting the light, wherein the center of the light source part coincides with the center of the pipe in the cross-sectional view, whereby a distance from the center to the inner circumferential surface is constant at any position and wherein a number of the light source units is n, with n being three or more, and the substrates of the light source units correspond to each side of a regular n-polygon when viewed in a cross-section; wherein a ratio of a first distance between two light sources adjacent to each other to a second distance from each light source to an inner circumferential surface of the pipe ranges from 1:0.8 to 1: 1.25 when viewed in a longitudinal-section, wherein the first distance is set so that an amount of light at a point, which is an intermediate point between a first point on the inner surface of the pipe perpendicular to a first light source and a third point on the inner surface of the pipe perpendicular to a second light source adjacent to the side of the first light source, is equal to or greater than about 70%, preferably equal to or greater than 80%, of the amount of light at the first point and third point. a pipe comprising an inlet and an outlet and comprising an internal space through which a fluid moves; and a light source part disposed in the internal space and providing a light in the ultraviolet wavelength band to the fluid, the light source part comprising at least one light source unit comprising a substrate extending along a predetermined direction and a plurality of light sources disposed on the substrate along the predetermined direction, the light sources being light emitting diodes and emitting the light, wherein the center of the light source part coincides with the center of the pipe in the cross-sectional view, whereby a distance from the center to the inner circumferential surface is constant at any position and wherein a number of the light source units is n, with n being three or more, and the substrates of the light source units correspond to each side of a regular n-polygon when viewed in a cross-section; wherein a ratio of a first distance between two light sources adjacent to each other to a second distance from each light source to an inner circumferential surface of the pipe ranges from 1:0.8 to 1: 1.25 when viewed in a longitudinal-section, wherein the first distance is set so that an amount of light at a point, which is an intermediate point between a first point on the inner surface of the pipe perpendicular to a first light source and a third point on the inner surface of the pipe perpendicular to a second light source adjacent to the side of the first light source, is equal to or greater than about 70%, preferably equal to or greater than 80%, of the amount of light at the first point and third point.