A sample feeding device for a trace detector is disclosed. The sample feeding device comprises: a sample feeding chamber disposed in the sample feeding device to desorb a sample from a sample feeding member; and a valve assembly configured to fluidly communicate the sample feeding chamber with a drift tube of the trace detector during feeding sample. With the above configuration of the present invention, for example, the sensitivity of the detector can be increased by improving the permeation ratio of the sample. In addition, interior environment of the drift tube is isolated from exterior environment to avoid a drift region of the drift tube from being polluted. The important parameters, such as sensitivity, a position of a peak of a substance, a resolution, of the detector can be kept constant. As a result, operation reliability and consistency of the detector can be achieved.