A fluid treatment device including: a pipe having an inlet through which fluid is introduced into the pipe from a fluid treatment space, an outlet through which sterilized fluid is discharged to the fluid treatment space, and a flow channel connecting the inlet to the outlet, the pipe providing a sterilization area in the flow channel; a solvent filling at least a portion of the sterilization area; and at least one light source module disposed in the sterilization area, and including a light source to emit sterilizing light and a substrate on which the light source is mounted, in which the fluid introduced through the inlet passes through the solvent towards the outlet, the solvent traps contaminants contained in the fluid when the fluid passes through the solvent, and the light source module sterilizes the solvent with the contaminants trapped therein.