A heater for top portions of containers 11 filled with contents and each having a top forming tubular portion 14 generally rectangular to square in cross section for heating seal parts 31, 35 of the top forming portion 14 with hot air for heat-sealing comprises a hot air nozzle 51 in the form of a bottomed tube having a generally rectangular to square cross section and to be inserted into the top forming portion 14 for heating. The hot air nozzle 51 having first to fourth four side walls 61 to 64 integral with one another with a ridgeline formed between the adjoining side walls. The side walls 61 to 64 is formed with orifices 68 as distributed over regions thereof corresponding to the respective seal parts 31, 35. The side walls 61 to 64 each have an outer surface facing obliquely upward.
A heating device for heat-sealing containers by heating an end forming portion 13 of a tubular container having a rectangular to square cross section, the end forming portion 13 having four generally quadrilateral first to fourth panels 21 to 24 continuous with one another and each having a heating region 31, 32, 33 or 34 to be heated on an inner surface thereof. The heating device has a hot air nozzle 71 in the form of a bottomed tube and fittable into the container end forming portion 13 for heating an inner surface of the container. The nozzle 71 has four side walls 81 to 84 continuous with one another and corresponding to the first to fourth panels 21 to 24 respectively, at least one of the side walls 81 to 84 being provided with a hot air discharge portion 121, 122, 123 or 124 having orifices 111 and to be opposed to the heating region of the corresponding panel 21, 22, 23 or 24 and with a hot air nondischarge portion 125, 126, 127 or 128 other than the discharge portion, the hot air nondischarge portion being at least partly provided with a hot air escape portion 95, 96, 97 or 98.
