The invention relates to a thermal cutter for plastic materials. The thermal cutter for the plastic material comprises a cutter bit made of heat conduction materials. A containing cavity used for containing the cut plastic materials is formed in the bottom of the cutter bit and is provided with a downward opening. The edge of the opening of the containing cavity is provided with a downward cutting edge, and a cutter bit heating device used for heating the cutter bit is further arranged in the cutter bit. By means of the structure, the cutter bit heating device can be used for heating the cutter bit to melt plastics to be machined, and meanwhile the downward cutting edge can be used for cutting the plastics to be machined; due to the cooperation of heating and the cutting edge, the parts which are cut off can enter the containing cavity and are separated from the base materials of the plastics to be machined; the structure is simple, and cost is low; and in addition, compared with manual cutting, repeated cutting is not needed, the cutting quality can be improved easily, and the working efficiency can also be improved.