A method of producing beta-glucan, insoluble food fibre and protein preparation from oat bran, encompassing the following steps: - the raw material is transported into the container, where water and ethanol are added from container via pump, whereafter such a suspension is mixed at a temperature from 50°C to 100°C, preferably from 70°C to 80°C; - cooling is performed using water from the cooling device and the suspension is directed onto the vibrating sieve; - the ethanol-containing filtrate from the sieve is sent to the ethanol recovery station, where the ethanol is distilled off, is then returned via pump to container, and the ethanol-recovery broth is concentrate d by evaporating off excess water and the resulting broth is directed via pump to container, whereas the concentrated bran fraction remaining on the sieve is directed to container, where it is suspended in water and NaOH solution supplied by pump from container, and then the suspension is mixed at a temperature of 50°C to 100°C, preferably from 70°C to 80°C; - after cooling with water from the cooling device, the suspension is directed onto the vibrating sieve via pump and the separated solids are directed to container, where they are mixed with the broth, whereas the filtrate obtained from sieve is directed to container, where it is acidified using HCl, and the protein fraction is subsequently precipitated out; - the liquid from container is directed by pump to the centrifuge, where the protein fraction is separated, which is then transferred onto the tray drier and the protein is directed for apportionment following drying; - the supernatant resulting from centrifugation is directed to container, where it is neutralised by an addition of NaOH solution supplied via pump from container and then, after neutralisation, and addition of ethanol from container via pump causes the precipitation of beta-glucan in the container; - the suspension is directed onto the vibrating sieve via pump, where the separated, solid beta-glucan is directed to container, where it is suspended in a small quantity of ethanol supplied from container via pump, and then pump directs it to the spray drier, whereafter it is further directed for apportionment; - the filtrate obtained from sieve, containing ethanol is directed do the alcohol recovery station, where the ethanol is distilled off, which is then returned via pump to container, and then the ethanol recovery broth is concentrated via the evaporation of water and such a resulting liquid is directed via pump to container, where it is mixed with the remaining components, and the resulting suspension is directed via pump to the tray drier, where the dried preparation of insoluble food fibre is directed for apportionment. - the raw material is transported into the container, where water and ethanol are added from container via pump, whereafter such a suspension is mixed at a temperature from 50°C to 100°C, preferably from 70°C to 80°C; - cooling is performed using water from the cooling device and the suspension is directed onto the vibrating sieve; - the ethanol-containing filtrate from the sieve is sent to the ethanol recovery station, where the ethanol is distilled off, is then returned via pump to container, and the ethanol-recovery broth is concentrate d by evaporating off excess water and the resulting broth is directed via pump to container, whereas the concentrated bran fraction remaining on the sieve is directed to container, where it is suspended in water and NaOH solution supplied by pump from container, and then the suspension is mixed at a temperature of 50°C to 100°C, preferably from 70°C to 80°C; - after cooling with water from the cooling device, the suspension is directed onto the vibrating sieve via pump and the separated solids are directed to container, where they are mixed with the broth, whereas the filtrate obtained from sieve is directed to container, where it is acidified using HCl, and the protein fraction is subsequently precipitated out; - the liquid from container is directed by pump to the centrifuge, where the protein fraction is separated, which is then transferred onto the tray drier and the protein is directed for apportionment following drying; - the supernatant resulting from centrifugation is directed to container, where it is neutralised by an addition of NaOH solution supplied via pump from container and then, after neutralisation, and addition of ethanol from container via pump causes the precipitation of beta-glucan in the container; - the suspension is directed onto the vibrating sieve via pump, where the separated, solid beta-glucan is directed to container, where it is suspended in a small quantity of ethanol supplied from container via pump, and then pump directs it to the spray drier, whereafter it is further directed for apportionment; - the filtrate obtained from sieve, containing ethanol is directed do the alcohol recovery station, where the ethanol is distilled off, which is then returned via pump to container, and then the ethanol recovery broth is concentrated via the evaporation of water and such a resulting liquid is directed via pump to container, where it is mixed with the remaining components, and the resulting suspension is directed via pump to the tray drier, where the dried preparation of insoluble food fibre is directed for apportionment.