ABM liquid inoculant for beans – a bio-preparation based on Rhizobium leguminosarum biovar vicinalis. The active substance is present in an amount of not less than 7.5*108 CFU/ml and constitutes 4% of the total volume of the preparation. The preparation is intended for seed treatment of beans to increase yield by fixing atmospheric nitrogen through bacteria included in the inoculant. Treatment is performed once at a rate of 0.25 kg per 100 kg of seeds or 0.5 kg per 100 kg of seeds under unfavorable growing conditions, such as soil with low organic matter content, high acidity or alkalinity, as well as in cases of soil erosion, drought or flooding. The preparation is intended for use in agriculture and ensures effective rooting of plants and development of the root system.