This invention relates to a non-touch type heater for heating a synthetic filament yarn, especially a polyester filament yarn, in a false-twist texturing process while keeping the running yarn apart from a heater surface. According to the invention the heater comprises a heater body having a lengthwise groove in the surface thereof with a plurality of yarn guides being arranged in said groove so that the yarn runs along an arcuate path defined by the yarn guides. Further, according to the invention, the distance between the heater surface and the yarn path is minimum at the inlet and exit ends of the path and maximum in the middle of said path.