An apparatus for synthesizing nanotubes is provided. The apparatus includes a reactor, a first electrode and a second electrode, and an actuator. The reactor is configured for receiving a catalyst used for growing nanotubes. The first electrode and the second electrode are disposed in the reactor and configured for generating an electric field therebetween. The second electrode is spaced apart from the first electrode and movable relative to the first electrode along a direction perpendicular to another direction oriented from the first electrode to the second electrode. The actuator is configured for adjusting a direction of the electric field generated by the first electrode and the second electrode.