The invention discloses a flexible tape welding device. The flexible tape welding device comprises a bottom plate, a circuit board, a circuit board grip slipper, an electromagnet, an electromagnet fixing seat, a flexible tape clamp and a pressure plate, wherein the circuit board grip slipper and the electromagnet fixing seat are mounted on the bottom plate; the pressure plate and the flexible tape clamp are made of materials capable of being attracted magnetically; two ejector pins are arranged at the front end of the pressure plate; and the directions of the ejector pins are perpendicular to the circuit board. The invention further relates to a welding method. The welding method comprises the following steps: fixing the circuit board on the circuit board grip slipper, and clamping a flexible tape by using the flexible tape clamp; attaching the flexible tape clamp to the surface of the electromagnet which is not electrified; manually adjusting matched alignment of a flexible tape bonding pad and a circuit board bonding pad, and electrifying the electromagnet to fix the flexible tape clamp; and placing the pressure plate on the surface of the flexible tape clamp so that end surfaces of the two ejector pins at the front end of the pressure plate drop to the surface of the flexible tape, and operating soldering iron and solder wires to carry out welding by a single person at the moment. The flexible tape welding device is simple to operate, the position is adjusted conveniently, welding accuracy is high, and the production efficiency is improved remarkably.