A circular saw blade to cut electric resistance welded pipes in the electric resistance welded pipe production line experiences an excessive load on hard tips thereof because of the limited cutting time, which results in reduced durability and chipping.[Solution] A flank 18 is provided with a first flank 20 located at the center thereof, and second and third flanks 22, 24 located inclined toward the respective sides of the first flank 20. Therefore, the lateral sides of the flank 18 have a constant clearance angle rearward from a cutting edge 34, which provides advantages of increased strength and resistance to chipping. Furthermore, a fourth flank 26 having a larger clearance angle is separately provided at the rear of the first flank 20 located at the center. Even if the first flank 20 wears, it is possible to reduce the wear on the fourth flank 26 and improve the durability.