A carbon nanotube synthesizing apparatus in which the state of generated plasma can be stabilized is provided. A carbon nanotube synthesizing apparatus 1 comprises a chamber 2, an antenna 3 including a tip 3a, a microwave conductor 4, a gas introducing unit 5, a gas discharging unit 6, a substrate holding unit 7, and a heating unit 8. The shape of the inner wall of the chamber 2 is symmetrical with respect to the tip 3a of the antenna 3.