A hole saw includes a circular saw blade and a cover plate. The circular saw blade is made by rounding a lengthwise rectangular metal sheet and connecting two ends thereof to define therein an accommodating space. The circular saw blade has one edge provided with a plurality of sawteeth and an opposite edge provided with a connecting portion. The cover plate covers the connecting portion of the circular saw blade and has a base, a positioning portion and a shoulder. The positioning portion extends from the base toward the connecting portion. The shoulder is formed between the base and the positioning portion. Thereby, the hole saw has advantages about low manufacturing costs and short production cycle. Besides, since the shoulder increases contacting area between the circular saw blade and the cover plate, the structural firmness of the soldered hole saw is improved.