A heat insulating device for a pipe according to the present invention comprises: a pair of heat insulation materials which respectively surround the outer surfaces of one side and the other side of a pipe in the radial direction; a plurality of reflectors which surround the outer surfaces of the heat insulation materials and are arranged spaced a predetermined distance from each other; a pair of outer heat insulation materials which surround the outer surface of the outermost reflector among the plurality of reflectors; a pair of aluminum covers which surround the outer surfaces of the outer heat insulation materials; out-profiles which are coupled so as to surround both ends of the aluminum covers in the width direction; in-profiles which are coupled so as to surround both ends of the aluminum covers in the longitudinal direction; and heat resistant fibers for covering externally exposed portions of the heat insulation materials and the outer heat insulation materials. Compared to a heat insulating device composed of only heat insulation materials, the heat insulating device which is for a pipe and provided with reflectors according to the present invention has excellent heat insulating performance, is easy to maintain and repair due to it being possible to partially replace the heat insulation materials, and has a simple inner configuration, and thus has the advantages of being easy to manufacture and having excellent durability.