Noise diagnostics has been performed on the cold field-emission cathode in high-vacuum. The tested cold field-emission cathode, based on tungsten wire with ultra-sharp tip coated by epoxy was designed to meet the requirements of transmission electron microscopy, which uses a small and stable source of electrons. Current fluctuations are reduced by improving the structure and fabrication technology. Noise was measured both in time and frequency domains, which gives information about current fluctuations and also about charge transport. Mutual correlation between the noise spectral density, extractor voltage and beam brightness was analyzed.