The invention provides a high frequency sewing machine. A to-be-processed piece is conveyed in a manner of being clamped by an upper annular band and a lower annular band. At the same time, high frequency power is applied to positive and negative electrodes arranged oppositely in the upper and lower positions of a conveying path of the to-be-processed piece. Thus, a hot plastic resin is fused due to medium heating. A coincide part of fiber material is bonded continuously by adhesive agent of the fusing band. A film is adhered to the electrode face of the negative electrode and a preheating effect is achieved through heat generation of the film. The machine is also provided with an action control part enabling the upper and the lower annular band to convey and to perform specified bonding processing when the two electrodes are heated to a specified temperature after the actions start. Therefore, pressing trace and overheat trace can be inhibited and a structure for protecting an electrode face can be utilized effectively, so that peripheral structure of the electrodes can be simplified and small size is realized. Besides, a preheating effect enabling the electrodes to keep in a high temperature state is generated. Deviation-free bonding processing with good reliability and stability in the whole length of the to-be-processed piece is achieved.