The utility model discloses an adjustable quartz tube bending device. The adjustable quartz tube bending device comprises a rack, an electric motor, a friction belt pulley, a transmission shaft, a clutch gear, a main shaft gear, a main shaft, a rotary table, a rotary arm, a pipe clamp, fire heads, a bracket and an electric control box, wherein the electric motor is arranged in the bracket; the friction belt pulley is connected with the electric motor; the friction belt pulley, the transmission shaft, the clutch gear, the main shaft gear, the main shaft, the rotary table, the rotary arm and the pipe clamp are connected with one another in sequence; the fire heads are arranged in the bracket; the rotating radius of the rotary arm is adjustable in the range of 20mm-240mm; a quartz tube rotates along with the rotary arm with set bending radius and bends automatically. Therefore, the product quality and yield are greatly improved, the manpower is reduced, the labor intensity is reduced, and the product application range is wide.