The invention discloses an ultrahigh-frequency signal detection device and a partial discharge detection device. The ultrahigh-frequency signal detection device comprises a dielectric substrate, a metal patch and a feeder pillar. The dielectric substrate is provided with a first surface and a second surface which corresponds to the first surface; the rectangular metal patch is fixed onto the first surface of the dielectric substrate and is used for detecting ultrahigh-frequency signals; the elongated feeder pillar is fixed into the dielectric substrate, a first end of the feeder pillar is connected with the metal patch, and a second end of the feeder pillar is used for outputting the ultrahigh-frequency signals. The ultrahigh-frequency signal detection device and the partial discharge detection device have the advantages that the problem of large size of an ultrahigh-frequency signal detection device in the prior art can be solved; a sensor can be lightened and is portable.