To provide a rotary sawing machine keeping a working environment clean by obtaining an effect of collecting chip dust to a high degree.

The rotary sawing machine includes a base seat, a saw blade seat and a saw blade cover. At least one first convection hole is formed on one side corresponding to an opening of the saw blade seat, and at least one second convection hole generating an air flow matching the first convection hole is formed in a wall surface facing a saw blade of the saw blade cover. The air flow is thereby accelerated, and chip dust caused by cutting with the rotary saw is completely retained within the saw blade cover to effectively improve dust collecting efficiency. Covering sheets allowing only the saw blade to pass through and improving air current convection efficiency are extended from the saw blade seat and the saw blade cover respectively toward the saw blade. Since only the saw blade can pass through the opening, dust collecting efficiency is greatly improved.