Disclosed are a substrate treating apparatus and a fluid supply unit that reduce the outer diameter while preventing condensation from occurring even without wrapping a pipe supplying a refrigerant with a heat insulating material. The substrate treating apparatus includes: a process chamber having a treatment space for treating a substrate; an inner pipe connected to the process chamber and for supplying a heat exchange fluid to an interior of the process chamber; a cooler connected to the inner pipe, and for cooling the heat exchange fluid and supplying the cooled heat exchange fluid to the inner pipe; an outer pipe disposed on an outer side of the inner pipe while surrounding the inner pipe to form a suction space between the inner pipe and the outer pipe; an intake part connected to the suction space, and for sucking the suction space; and a spacing maintaining part disposed in the suction space, and for maintaining a spacing distance between the inner pipe and the outer pipe.