The invention discloses a sideband suppression method comprising the following steps of: A, determining a positive vortex correction factor and a negative vortex correction factor; adopting a positive gradient to scan in N/2 times; respectively collecting positive gradient scanning signals in each scanning time; adopting a negative gradient to scan in N/2 times; respectively collecting negative gradient scanning signals in each scanning time, wherein N is an even number; carrying out the vortex correction of the collected H/2 positive gradient scanning signals according to the positive vortexcorrection factor; and carrying out the vortex correction of the collected H/2 negative gradient scanning signals according to the negative vortex correction factor; and B, calculating spectrum signals through sideband suppression according to the vortex-corrected H/2 positive gradient scanning signals and the vortex-corrected H/2 negative gradient scanning signals. And meanwhile, the invention also discloses a sideband suppression device. The sideband suppression method and the sideband suppression device can effectively suppress sidebands.